I have an OUTSTANDING Lender that you should probably talk to. She has worked miracles in the past for people that credit in the 500's. She also has a BUNCH of down payment assistance options, which could minimize any down payment, or (in many situations) completely cover your down payment. These programs are basically FREE MONEY!!! (grants, etc - that you DO NOT have to pay back). I'd love to help you through the process of obtaining a loan and achieving home ownership, especially while prices and interest rates are still low!
Let me know if I can help get you started :)