What investments work for these goals?
If you will leave the money invested for a good long while (years) then dividend paying stocks would be appropriate. There are many that pay yields of 3 to 4 percent, which you can take as income or reinvest to compound the growth. There is a lot of good analysis of stocks (and mutual funds that specialize in dividend paying stocks) at Morningstar.com Assuming this will be a taxable account (since you want to pull income off of it, although this will lower wealth growth), you could open a brokerage account at some place like Vanguard (free on their ETFs) and look at tax efficient index fund ETFs (such as total stock market or their 500 fund), including  some international (foreign tax credit is nice in taxable) and muni funds for the (tax advantaged) income, although CDs are likely better for the income at this point.
Okay, I think I managed to find the precise answer to this problem! It involves solving a non-linear exponential equation, but I also found a good approximate solution using the truncated Taylor series. See below for a spreadsheet you can use. Let's start by defining the growth factors per period, for money in the bank and money invested:   Now, let S be the amount ready to be invested after n+1 periods; so the first of that money has earned interest for n periods. That is,  The key step to solve the problem was to fix the total number of periods considered. So let's introduce a new variable: t = the total number of time periods elapsed So if money is ready to invest every n+1 periods, there will be t/(n+1) separate investments, and the future value of the investments will be:  This formula is exact in the case of integer t and n, and a good approximation when t and n are not integers. Substituting S, we get the version of the formula which explicitly depends on n:  Fortunately, only a couple of terms in FV depend on n, so we can find the derivative after some effort:  Equating the derivative to zero, we can remove the denominator, and assuming t is greater than zero, we can divide by the constant ( 1-G t ):  To simplify the equation, we can define some extra constants:    Then, we can define a function f(n) and write the equation as:  Note that α, β, γ, G, and R are all constant. From here there are two options: Use Newton's method or another numerical method for finding the positive root of f(n). This can be done in a number of software packages like MATLAB, Octave, etc, or by using a graphics calculator. Solve approximately using a truncated Taylor series polynomial. I will use this method here. The Taylor series of f(n), centred around n=0, is:  Truncating the series to the first three terms, we get a quadratic polynomial (with constant coefficients):  Using R, G, α, β and γ defined above, let c0, c1 and c2 be the coefficients of the truncated Taylor series for f(n):    Then,  n should be rounded to the nearest whole number. To be certain, check the values above and below n using the formula for FV. Using the example from the question: For example, I might put aside $100 every week to invest into a stock   with an expected growth of 9% p.a., but brokerage fees are $10/trade.   For how many weeks should I accumulate the $100 before investing, if I   can put it in my high-interest bank account at 4% p.a. until then? Using Newton's method to find roots of f(n) above, we get n = 14.004. Using the closed-form approximate solution, we get n = 14.082. Checking this against the FV with t = 1680 (evenly divisible by each n + 1 tested): Therefore, you should wait for n = 14 periods, keeping that money in the bank, investing it together with the money in the next period (so you will make an investment every 14 + 1 = 15 weeks.) Here's one way to implement the above solution with a spreadsheet. StackExchange doesn't allow tables in their syntax at this time, so I'll show a screenshot of the formulae and columns you can copy and paste: Formulae:  Copy and paste column A: Copy and paste column B: Results:  Remember, n is the number of periods to accumulate money in the bank. So you will want to invest every n+1 weeks; in this case, every 15 weeks. What is your investing goal? And what do you mean by investing? Do you necessarily mean investing in the stock market or are you just looking to grow your money? Also, will you be able to add to that amount on a regular basis going forward? If you are just looking for a way to get $100 into the stock market, your best option may be DRIP investing. (DRIP stands for Dividend Re-Investment Plan.) The idea is that you buy shares in a company (typically directly from the company) and then the money from the dividends are automatically used to buy additional fractional shares. Most DRIP plans also allow you to invest additional on a monthly basis (even fractional shares). The advantages of this approach for you is that many DRIP plans have small upfront requirements. I just looked up Coca-cola's and they have a $500 minimum, but they will reduce the requirement to $50 if you continue investing $50/month. The fees for DRIP plans also generally fairly small which is going to be important to you as if you take a traditional broker approach too large a percentage of your money will be going to commissions. Other stock DRIP plans may have lower monthly requirements, but don't make your decision on which stock to buy based on who has the lowest minimum: you only want a stock that is going to grow in value. They primary disadvantages of this approach is that you will be investing in a only a single stock (I don't believe that can get started with a mutual fund or ETF with $100), you will be fairly committed to that stock, and you will be taking a long term investing approach. The Motley Fool investing website also has some information on DRIP plans : http://www.fool.com/DRIPPort/HowToInvestDRIPs.htm . It's a fairly old article, but I imagine that many of the links still work and the principles still apply If you are looking for a more medium term or balanced investment, I would advise just opening an online savings account. If you can grow that to $500 or $1,000 you will have more options available to you. Even though savings accounts don't pay significant interest right now, they can still help you grow your money by helping you segregate your money and make regular deposits into savings. There are ETFs listed on the Brazilian stock market. Specifically there is one for S&P500 - SPXI11, which might fulfill your requirements, though as one commenter has observed, it doesn't answer your original question. You could certainly look at the holdings of index funds and choose index funds that meet your qualifications.  Funds allow you to see their holdings, and in most cases you can tell from the description whether certain companies would qualify for their fund or not based on that description - particularly if you have a small set of companies that would be problems. You could also pick a fund category that is industry-specific. I invest in part in a Healthcare-focused fund, for example.  Pick a few industries that are relatively diverse from each other in terms of topics, but are still specific in terms of industry - a healthcare fund, a commodities fund, an REIT fund.  Then you could be confident that they weren't investing in defense contractors or big banks or whatever you object to. However, if you don't feel like you know enough to filter on your own, and want the diversity from non-industry-specific funds, your best option is likely a 'socially screened' fund like VFTSX is likely your best option; given there are many similar funds in that area, you might simply pick the one that is most similar to you in philosophy. "I'd suggest you to separate ""doing good"" from ""earning profit"". Look at the guys like Warren Buffett and Bill Gates (or Carnegie and Ford for that matters). They understand that you can't reconcile the two goals, so they donate for free what they earned for profit. If you want to make a social impact with your money, you can check the charity programs that have a confirmed record of a positive impact on people's lives. Non-profits that studied such programs publish their results extensively: AidGrade compiles this research and suggests direct donations to the programs that demonstrated best outcomes per dollar invested:" Personally, I invest in mutual funds.  Quite a bit in index funds, some in capital growth & international. For a time period as short as a matter of months, commercial paper or bonds about to mature are the highest returning investments, as defined by Benjamin Graham:  An investment operation is one which, upon thorough analysis, promises safety of principal and a satisfactory return. Operations not meeting these requirements are speculative. There are no well-known methods that can be applied to cryptocurrencies or forex for such short time periods to promise safety of principal. The problem is that with $1,500, it will be impossible to buy any worthy credit directly and hold to maturity; besides, the need for liquidity eats up the return, risk-adjusted.  The only alternative is a bond ETF which has a high probability of getting crushed as interest rates continue to rise, so that fails the above criteria. The only alternative for investment now is a short term deposit with a bank. For speculation, anything goes... The best strategy is to take the money and continue to build up a financial structure: saving for risk-adjusted and time-discounted future annual cash flows.  After the average unemployment cycle is funded, approximately six or so years, then long-term investments should be accumulated, internationally diversified equities. So I did some queries on Google Scholar, and the term of art academics seem to use is target date fund. I notice divided opinions among academics on the matter. W. Pfau gave a nice set of citations of papers with which he disagrees, so I'll start with them. In 1969, Paul Sameulson published the paper Lifetime Portfolio Selection By Dynamic Stochaistic Programming, which found that there's no mathematical foundation for an age based risk tolerance. There seems to be a fundamental quibble relating to present value of future wages; if they are stable and uncorrelated with the market, one analysis suggests the optimal lifecycle investment should start at roughly 300 percent of your portfolio in stocks (via crazy borrowing). Other people point out that if your wages are correlated with stock returns, allocations to stock as low as 20 percent might be optimal. So theory isn't helping much. Perhaps with the advent of computers we can find some kind of empirical data. Robert Shiller authored a study on lifecycle funds when they were proposed for personal Social Security accounts. Lifecycle strategies fare poorly in his historical simulation: Moreover, with these life cycle portfolios, relatively little is contributed when the allocation to stocks is high, since earnings are relatively low in the younger years. Workers contribute only a little to stocks, and do not enjoy a strong effect of   compounding, since the proceeds of the early investments are taken out of the stock   market as time goes on. Basu and Drew follow up on that assertion with a set of lifecycle strategies and their contrarian counterparts: whereas a the lifecycle plan starts high stock exposure and trails off near retirement, the contrarian ones will invest in bonds and cash early in life and move to stocks after a few years. They show that contrarian strategies have higher average returns, even at the low 25th percentile of returns. It's only at the bottom 5 or 10 percent where this is reversed. One problem with these empirical studies is isolating the effect of the glide path from rebalancing. It could be that a simple fixed allocation works plenty fine, and that selling winners and doubling down on losers is the fundamental driver of returns. Schleef and Eisinger compare lifecycle strategy with a number of fixed asset allocation schemes in Monte Carlo simulations and conclude that a 70% equity, 30% long term corp bonds does as well as all of the lifecycle funds. Finally, the earlier W Pfau paper offers a Monte Carlo simulation similar to Schleef and Eisinger, and runs final portfolio values through a utility function designed to calculate diminishing returns to more money. This seems like a good point, as the risk of your portfolio isn't all or nothing, but your first dollar is more valuable than your millionth. Pfau finds that for some risk-aversion coefficients, lifecycles offer greater utility than portfolios with fixed allocations. And Pfau does note that applying their strategies to the historical record makes a strong recommendation for 100 percent stocks in all but 5 years from 1940-2011. So maybe the best retirement allocation is good old low cost S&P index funds! "Warren Buffett: 'Investing Advice For You--And My Wife' (And Other Quotes Of The Week): What I advise here is essentially identical to certain instructions   I’ve laid out in my will. One bequest provides that cash will be   delivered to a trustee for my wife’s benefit…My advice to the trustee   could not be more simple: Put 10% of the cash in short-term government   bonds and 90% in a very low-cost S&P 500 index fund. (I suggest   Vanguard’s.) I believe the trust’s long-term results from this policy   will be superior to those attained by most investors… Similarly from Will Warren Buffett's investment advice work for you?: Specifically, Buffett wants the trustee of his estate to put 10   percent of his wife's cash inheritance in short-term government bonds   and 90 percent in a low-cost S&P index fund - and he tips his hat   specifically to Bogle's Vanguard in doing so. Says Buffett: ""I believe   the trust's long-term results from this policy will be superior to   those attained by most investors - whether pension funds, institutions   or individuals.""" This is a very interesting question. I'm going to attempt to answer it. Use debt to leverage investment. Historically, stock markets have returned 10% p.a., so today when interest rates are very low, and depending on which country you live in, you could theoretically borrow money at a very low interest rate and earn 10% p.a., pocketing the difference. This can be done through an ETF, mutual funds and other investment instruments. Make sure you have enough cash flow to cover the interest payments! Similar to the concept of acid ratio for companies, you should have slightly more than enough liquid funds to meet the monthly payments. Naturally, this strategy only works when interest rates are low. After that, you'll have to think of other ideas. However, IMO the Fed seems to be heading towards QE3 so we might be seeing a prolonged period of low interest rates, so borrowing seems like a sensible option now. Since the movements of interest rates are political in nature, monitoring this should be quite simple. It depends on you. Since interest rates are the opportunity cost of spending money, the lower the interest rates, the lower the opportunity costs of using money now and repaying it later. Interest rates are a market mechanism so that people who prefer to spend later can lend to people who prefer to spend now for the price of interest. *Disclaimer: Historically stocks have returned 10% p.a., but that doesn't mean this trend will continue indefinitely as we have seen fixed income outperform stocks in the recent past. There's a few different types of investments you could do. As poolie mentioned, you could split your money between the Vanguard All World ex-US and Vanguard Total Stock Market index. A similar approach would be to invest in the Vanguard Total World Stock ETF. You wouldn't have to track separate fund performances, at the downside of not being able to allocate differential amounts to the US and non-US markets (Vanguard will allocate them by market cap). You could consider investing in country-specific broad market indices like the S&P 500 and FTSE 100. While not as diversified as the world indices, they are more correlated with the country's economic outlook. Other common investing paradigms are investing in companies which have historically paid out high dividends and companies that are under-valued by the market but have good prospects for future growth. This gets in the domain of value investing, which an entire field by itself. Like Andrew mentioned, investing in a mutual fund is hassle-free. However, mutual fees/commissions and taxes can be higher (somewhere in the range 1%-5%) than index funds/ETF expense ratios (typically <0.50%), so they would have to outperform the market by a bit to break-even. There are quite a few good books out there to read up about investing. I'd recommend The Intelligent Investor and Millionaire Teacher to understand the basics of long-term investing, but of course, there are many other equally good books too. "You don't state a long term goal for your finances in your message, but I'm going to assume you want to retire early, and retire well. :-) any other ideas I'm missing out on? A fairly common way to reach financial independence is to build one or more passive income streams.  The money returned by stock investing (capital gains and dividends) is just one such type of stream.  Some others include owning rental properties, being a passive owner of a business, and producing goods that earn long-term royalties instead of just an immediate exchange of time & effort for cash.    Of these, rental property is probably one of the most well-known and easiest to learn about, so I'd suggest you start with that as a second type of investment if you feel you need to diversify from stock ownership.  Especially given your association with the military, it is likely there is a nearby supply of private housing that isn't too expensive (so easier to get started with) and has a high rental demand (so less risk in many ways.)   Also, with our continued current low rate environment, now is the time to lock-in long term mortgage rates.  Doing so will reap huge benefits as rates and rents will presumably rise from here (though that isn't guaranteed.) Regarding the idea of being a passive business owner, keep in mind that this doesn't necessarily mean starting a business yourself.  Instead, you might look to become a partner by investing money with an existing or startup business, or even buying an existing business or franchise.  Sometimes, perfectly good business can be transferred for surprisingly little down with the right deal structure. If you're creative in any way, producing goods to earn long-term royalties might be a useful path to go down.  Writing books, articles, etc. is just one example of this.  There are other opportunities depending on your interests and skill, but remember, the focus ought to be on passive royalties rather than trading time and effort for immediate money.  You only have so many hours in a year.  Would you rather spend 100 hours to earn $100 every year for 20 years, or have to spend 100 hours per year for 20 years to earn that same $100 every year? .... All that being said, while you're way ahead of the game for the average person of your age ($30k cash, $20k stocks, unknown TSP balance, low expenses,) I'm not sure I'd recommend trying to diversify quite yet. For one thing, I think you need to keep some amount of your $30k as cash to cover emergency situations.  Typically people would say 6 months living expenses for covering employment gaps, but as you are in the military I don't think it's as likely you'll lose your job!  So instead, I'd approach it as ""How much of this cash do I need over the next 5 years?""  That is, sum up $X for the car, $Y for fun & travel, $Z for emergencies, etc.  Keep that amount as cash for now. Beyond that, I'd put the balance in your brokerage and get it working hard for you now.  (I don't think an average of a 3% div yield is too hard to achieve even when picking a safe, conservative portfolio.  Though you do run the risk of capital losses if invested.)  Once your total portfolio (TSP + brokerage) is $100k* or more, then consider pulling the trigger on a second passive income stream by splitting off some of your brokerage balance.  Until then, keep learning what you can about stock investing and also start the learning process on additional streams.  Always keep an eye out for any opportunistic ways to kick additional streams off early if you can find a low cost entry.   (*) The $100k number is admittedly a rough guess pulled from the air.  I just think splitting your efforts and money prior to this will limit your opportunities to get a good start on any additional streams.  Yes, you could do it earlier, but probably only with increased risk (lower capital means less opportunities to pick from, lower knowledge levels -- both stock investing and property rental) also increase risk of making bad choices." "In the UK, one quirky option in this area (OK, admittedly it's not a passive) is the ""Battle Against Cancer Investment Trust"" (BACIT).  Launched in 2012, it's basically a fund-of-funds where the funds held charge zero management charges or performance fees to the trust, but the trust then donates 1% of NAV to charity each year (half to cancer research, investors decide the other half)." Investing in mutual funds, ETF, etc. won't build a large pool of money. Be an active investor if your nature aligns. For e.g. Invest in buying out a commercial space (on bank finance) like a office space and then rent it out. That would give you better return than a savings account. In few years time, you may be able to pay back your financing and then the total return is your net return. Look for options like this for a multiple growth in your worth. Vanguard offers an index fund. Their FTSE Social Index Fund. For more information on it, go here.