Plan for the long term with your property investment Many entrepreneurs have either earned their money from property or, once they have built a business, have invested in a buy-to-let property. Building a property portfolio is very similar to building a business. You must know your target market and ensure what you offer tenants is better than that of your competition. Rental income is your turnover, which you need to maximise to make profit, and you need to understand all the costs of running a portfolio - including maintenance. In the experience of insurer Direct Line, many buy-to-let landlords underestimate the long-term cost of keeping a property up to scratch over 15 to 20 years. This can mean a new roof, damp proofing, electrics and kitchen, bathroom and window upgrades. It is also important to take care of little things such as clearing guttering and drains and checking walls for damp as well as making sure that the tenant is implementing security measures. Having good tradespeople on hand is vital so both your tenant and your property are well looked after.