The first thing you need to do is to understand very well the market, neighborhoods and the property type you will be investing in, their idiosyncrasies, current situation, and dynamics that is where prices and rents are headed (up or down) - if you are going to be investing in what I call "bargain" properties you need a mentor experienced in this type of investing (I am not one of those) because you will encounter many details turns and situations that are not described by books...You may check out the site www.getrealrei.com for information and guidance. Get a good feel of the market before doing anything.
Best of luck,