Both are great answers. Just wanted you to know I have leased several of my own houses before and have learned that some lenders will not count the leased home payment as debt against your income/debt ratio, so long as you have an enforceable lease agreement. However, each lender is different, as has been stated below. Any other point also, is to make sure the tenant pays you by check or money order or some way other than cash, so the lender can have copies of the payments being made by this third party. That is the proof, or "icing on the cake" that someone else is making the payments as claimed. This helps the underwriters determine your worthiness to acquire a new loan, sometimes! Remember you are still the liable party for the property, so that is why each lender treats this situation differently.
Let me know if I can point you toward some Lenders, that can help you, too. Anything else you need, please don't hesitate to ask.

Ryan is right you should talk to a lender about your options. There are so many factors that come into play that any answer we give you here would be incomplete.

It depends on many different factors, which include your income, your credit history, your downpayment, and many others. If you'd like to find out for sure, I'd be happy to refer you to some great lenders that would be happy to work with you without pressuring you into something. Just let me know.