You might want to look at an amortization table. Your principle isn't going to go down appreciably in the first 10 years. Consider this part of your research.
Brett
Agree with the above, plus it is a tough as nails rental market right now for landlords. There is just a ton of houses for rent right now. It is going to be tough for you to break even when you factor mortgage, insurance, expenses (wear and tear and damages), a property manager, and the general hassle of it all. You seem like you are approaching it smartly by taking your time, but use caution!