Optimal down payment amount
"The optimal down payment is 100%. The only way you would do anything else when you have the cash to buy it outright is to invest the remaining money to get a better return.  When you compare investments, you need to take risk into account as well.  When you make loan payments, you are getting a risk free return.  You can't find a risk-free investment that pays as much as your car loan will be.  If you think you can ""game the system"" by taking a 0% loan, then you will end up paying more for the car, since the financing is baked into the sales [price in those cases (there is no such thing as free money).  If you pay cash, you have much more bargaining power.   Buy the car outright (negotiating as hard as you can), start saving what you would have been making as a car payment as an emergency fund, and you'll be ahead of the game. For the inflation hedge - you need to find investments that act as an inflation hedge - taking a loan does not ""hedge"" against inflation since you'll still be paying interest regardless of the inflation rate.  The fact that you'll be paying slightly less interest (in ""real"" terms) does not make it a hedge. To answer the actual question, if your ""reinvestment rate"" (the return you can get from investing the ""borrowed"" cash) is less than the interest rate, then the more you put down, the greater your present value (PV). If your reinvestment rate is less than the interest rate, then the less you put down the better (not including risk).  When you incorporate risk, though, the additional return is probably not worth the risk. So there is no ""optimal"" down payment in between those mathematically - it will depend on how much liquid cash you need (knowing that every dollar that you borrow is costing you interest)." The optimal down payment is 0% IF your interest rate is also 0%. As the interest rate increases, so does the likelihood of the better option being to pay for the car outright. Note that this is probably a binary choice. In other words, depending on the rate you will pay, you should either put 0% down, or 100% down. The interesting question is what formula should you use to determine which way to go? Obviously if you can invest at a higher return than the rate you pay on the car, you would still want to put 0% down. The same goes for inflation, and you can add these two numbers together. For example, if you estimate 2% inflation plus 1% guaranteed investment, then as long as the rate on your car is less than 3%, you would want to minimize the amount you put down. The key here is you must actually invest it. Other possible reasons to minimize the down payment would be if you have other loans with higher rates- then obviously use that money to pay down those loans before the car loan. All that being said, some dealers will give you cash back if you pay for the car outright. If you have this option, do the math and see where it lands. Most likely taking the cash back is going to be more attractive so you don't even have to hedge inflation at all. Tip: Make sure to negotiate the price of the car before you tell them how you are going to pay for it. (And during this process you can hint that you'll pay cash for it.)
You are correct that 20% has an impact on your interest rate, although it is not always hugely significant.  You would have to do your own shopping around to find that information out.  However 20% has an impact that I consider to be far more important than your monthly payment, and that is in your equity.  If the DC market tanks, which I know it has not really done like much of the country but none of us have crystal balls to know if it will or not, then you will be more easily underwater the less you put down.  Conversely putting 20% or more down makes you an easy sell to lenders [i]and[/i] means that you don't have to worry nearly so much about having to do a short sale in the future. I would never buy a house with less than 20% down personally and have lived well below my means to get there, but I am not you. With regards to mortgages, the cheapskate way that I found information that I needed was to get books from the library that explained the mortgage process to me.  When it came time to select an actual broker I used my realtor's recommendation (because I trusted my realtor to actually have my interests at heart because he was an old family friend - you can't usually do that so I don't recommend it) and that of others I knew who had bought recently.  I compared four lenders and competed them against each other to get the best terms.  They will give you estimate sheets that help you weigh not only rates but costs of different fees such as the origination fee and discount points.  Make sure to know what fees the lender controls and what fees (s)he doesn't so that you know which lines to actually compare. Beyond a lender make sure that before closing you have found a title company that you think is a good choice (your realtor or lender will try to pick one for you because that's the way the business is played but it is a racket - pick one who will give you the best deal on title), a settlment company (may be title company, lender, or other) that won't charge you an excessive amount, a survey company that you like if required in DC for your title insurance, and homeowner's insurance coverage that you think is a good deal.  The time between contract and closing is short and nobody tells you to research all the closing costs that on a $500,000 place run to in excess of $10,000, but you should.  Also know that your closing costs will be about 2% of the purchase price and plan accordingly. In general take some time to educate yourself on homebuying as well as neighborhoods and price ranges.  Don't rush into this process or you will lose a lot of money fast. I am currently in the process of purchasing a house. I am only putting 5% down. I see that some are saying that the traditional 20% down is the way to go. I am a first time homebuyer, and unfortunately we no longer live in the world where 20% down is mandatory, which is part of the reason why housing prices are so high. I feel it is more important that you are comfortable with what your monthly payments are as well as being informed on how interest rates can change how much you owe each month. Right now interest rates are pretty low, and it would almost be silly to put 20% down on your home. It might make more sense to put money in different vehicle right now, if you have extra, as the global economy will likely pick up and until it does, interest rates will likely stay low. Just my 2 cents worth.  EDIT: I thought it would not be responsible of me not to mention that you should always have extra's saved for closing costs. They can be pricey, and if you are not informed of what they are, they can creep up on you. The relationship is not linear, and depends on a lot of factors. The term you're looking for is efficient frontier, the optimal rate of return for a given level of risk. The goal is to be on the efficient frontier, meaning that for the given level of risk, you're receiving the greatest possible rate of return (reward). http://www.investopedia.com/terms/e/efficientfrontier.asp The primary reason to put 20% down on your home is to avoid paying PMI (private mortgage insurance).  Anyone who buys a house with a down-payment of under 20% is required to pay for this insurance (which protects the lender in case you default on your loan). PMI is what enables people to buy homes with as little as 3-5% down. I would recommend against paying more than 20%, because having liquidity for emergency funds, or other investments will give you the sort of flexibility that's good to have when the economy isn't so great.  Depending on whether the house you purchase is move-in ready or a fixer-upper, having funds set aside for repairs is a good idea as well. In the United States a Jumbo Loan is one in which the loan amounts exceeds a set value. For much of the US it is currently $417,000 but it is higher in some areas. It is set by the US government and is adjusted each year.  If you are trying to avoid the Jumbo designation then putting more down makes that possible. Generally the Jumbo loans have a higher rate. My credit union does allow jumbo loans with less than 20% down, but I am not sure if they are in the majority or the minority regarding down payment requirements. Keep in Mind that once the house price goes above Jumbo/0.8 or $521,250 you will be putting down more than 20% to avoid the Jumbo designation. Your best bet is to talk with a banker about your specific plans.   One of the causes of the housing crash was an 80/20 loan.  There you would get a first for 80% of the value of a home and 20% on a HELOC for the rest.  This would help the buyer avoid PMI.  Editorially, the reason this was popular was because the buyer could not afford the home with the PMI and did not have a down payment.  They were simply cutting things too close. Could you find a banker willing to do something like this, I bet you could. In your case it seems like you are attempting to increase the value of your home by using money to do an improvement so the situation is better.  However, sizable improvements rarely return 100% or more on investments.  Typically, I would think, the bank would want you to have some money invested too.  So if you wanted to put in a pool, a smart banker would have you put in about 60% of the costs as pools typically have a 40% ROI.   However, I bet you can find a banker that would loan you 100%. You don't seem to be looking for advice on making a smart money decision, and it is difficult to render a verdict as very little detail is supplied about your specific situation. However, while certain decisions might look very profitable on paper, they rarely take into consideration risk. For a short term loan, the interest is closer to straight line, e.g. A $10K loan at 10% for 3 years will have approximately $1500 in interest. (The exact number is $1616, not too far off). You will save 2.41% on the rate, so you'll the extra payment you'll send to the mortgage will save you about 10000*35*(2.41/12)/2 or about $350 over the 3 year period. "TL;DR; There is no silver bullet. You have to decide how much to invest and when on your own.  Averaging down definition: DEFINITION of 'Average Down' The process of buying additional shares in a company at lower prices than you originally purchased. This brings the average price you've paid for all your shares down. BREAKING DOWN 'Average Down' Sometimes this is a good strategy, other times it's better to sell off a beaten down stock rather than buying more shares.  So let us tackle your questions: At what percentage drop of the stock price should I buy more shares. (Ex: should I wait for the price to fall by 5% or 10% to buy more.) It depends on the behaviour of the security and the issuer. Is it near its historical minimum? How healthy is the issuer? There is no set percentage. You can maximize your gains or your losses if the security does not rebound. Investopedia: The strategy is often favored by investors who have a long-term investment horizon and a contrarian approach to investing. A contrarian approach refers to a style of investing that is against, or contrary, to the prevailing investment trend.  (...) On the other side of the coin are the investors and traders who generally have shorter-term investment horizons and view a stock decline as a portent of things to come. These investors are also likely to espouse trading in the direction of the prevailing trend, rather than against it. They may view buying into a stock decline as akin to trying to ""catch a falling knife."" Your second question: How many additional shares should I buy. (Ex: Initially I bought 10 shares, should I buy 5,10 or 20.) That depends on your portfolio allocation before and after averaging down and your investor profile (risk apettite). Take care when putting more money on a falling security, if your portfolio allocation shifts too much. That may expose you to risks you shouldn't be taking. You are assuming a risk for example, if the market bears down like 2008: Averaging down or doubling up works well when the stock eventually rebounds because it has the effect of magnifying gains, but if the stock continues to decline, losses are also magnified. In such cases, the investor may rue the decision to average down rather than either exiting the position or failing to add to the initial holding.  One of the pitfalls of averaging down is when the security does not rebound, and you become too attached to be able to cut your losses and move on. Also if you are bullish on a position, be careful not to slip the I down and add a T on said position. Invest with your head, not your heart." "There are times that the simplest explanation (or analysis) is best.  You show that, for a time, the PMI is $1812/yr. And it's the cost you will incur by sending $15,000 to the student loan instead of using it as a downpayment. 1812/15000 is 12%. The loan is already costing you 4% (I know, 3.899, a rounding error), so in effect, that $15,000 is costing 16%. I doubt the student loan is even double digits.  Use the $15,000 toward the downpayment. Take the $1812 plus the $859 per year saved on the mortgage payment, and throw the $2671 towards the student loan. This is the simple solution. (Note: $15000 at 4% for 30 years is a payment of $71.61 or $859/yr.) Part of the PMI issue is that PMI gets removed when you hit 80% due to natural amortization. i.e. the timeframe due to normal payments. If you make extra payments, and hit 80% a year after you close, that's nice, but the bank will drag its feet, and the appraisal (at your cost) may come back low. Then what?  Last, without the S/L interest rate and term, I can't calculate the numbers the way your example showed, but don't mix up term and cash flow with actual cost. Say I owed my mom $50000, at zero interest, and $500/mo payment. Sending $50K would ""free up"" that $500/mo, but there are better uses for that money, such as high interest debt. You propose to create 16% debt in your scenario." "The loan is the loan, the down payment is not part of the loan.  The principle amount owed on the loan at the beginning of the loan is the amount of the loan. If your loan amount is $390,000 then that's below the ""jumbo"" classification.  Your down payment is irrelevant. Lenders may want or require 20% (or any other amount) down so the loan will meet certain ""loan to value"" ratio requirements. In the case of real estate the lenders in general want a 20% down side cushion before you're ""upside down"" (owe more than the home is worth). This is not unique to homes and is common in many secured lending instruments; like cars for example." "Say you're buying a 400K house. Your relative finances 120K (30%). Say I'm optimistic, but the real-estate market recovers, and your house is worth 600K in 5-6 years (can happen, with the inflation and all). The gain is 200K. Your relative gets 100K. You repay him 220K on 120K loan for 5 years. Roughly, 16% APR. Quite an expensive loan. I'm of course optimistic, it seems to me that so is your relative. The question is: if the house loses value in that term, does your relative take 50% of the losses? Make calculations based on several expected returns (optimistic, ""realistic"", loss case, etc), and for each calculate how much in fact will that loan cost. It will help you to decide if you want it. Otherwise your relationships with your relative might go very bad in a few years. BTW: Suggestion: it's a bad idea to mix business and friend/family you don't want to lose." A bigger down payment is good, because it insulates you from the swings in the real estate market.  If you get FHA loan with 3% down and end up being forced to move during a down market, you'll be in a real bind, as you'll need to scrape up some cash or borrow funds to get out of your mortgage. I'm of the belief that you should always put 20% down.  The lower interest rate will save you thousands over the life of the loan.  Also PMI is no different then burning that much cash in the fireplace every month. From Wikipedia Lenders Mortgage Insurance (LMI), also known as Private mortgage insurance (PMI) in the US, is insurance payable to a lender or trustee for a pool of securities that may be required when taking out a mortgage loan. It is insurance to offset losses in the case where a mortgagor is not able to repay the loan and the lender is not able to recover its costs after foreclosure and sale of the mortgaged property. You are basically paying money each month for the bank to be insured against you not paying your mortgage.  But in actuality the asset of the condo should be that insurance. Only you can decide if you are comfortable with having $50k in liquidity or not.  It sounds like a good cushion to me but I don't know the rest of your expenses. To optimize your return on investment, you need to buy low and sell high.  If you knew that one stock had hit rock bottom, and the others had not, buying the low stock would be the best. However, unless you can predict the future, you don't know if any individual stock has hit the bottom, or if it will continue to drop. If you decide to spend the same amount of money each month on stock purchases, then when the price is low, you will automatically buy more shares, and when the price is high, you will buy fewer shares.  This strategy is sometimes called dollar cost averaging.  It eliminates the need to predict the future to optimize your buying. All that having been said, I agree with @Powers that at the investment amount that you are talking about and the per transaction fee you listed, a monthly investment in several stocks will cause you to lose quite a bit to transaction fees.  It sounds like you need a different strategy. The answer depends on how much you spend every month. The DTI is calculated using the minimum payment on the balance owed on your card.  Credit card minimum payments are ridiculous, often being only $50 for balances of a couple thousand dollars. In any case, when you get preapproved, the lender will tell you (based on your DTI) the maximum amount they will approve you for. If your minimum payment is $50, that's another $50 that could go towards your mortgage, which could mean an additional $10,000 financed. It's up to you to decide if $10,000 will make enough of a difference in the houses you look at.