I'm going to be honest with you...Sellers that are willing to do the financing and take on the risk of dealing with any future foreclosures, don't take that risk lightly. What I've seen in the last year on those who are willing to do it, they are asking a minimum of 10% to 20% down and will be charging an 8% to 10% interest rate.
With current underwriting guidelines a 650 FICO is just over the minimum. It would be easy to do government financing, but conventional financing a little harder because they want higher scores. If you are taking a large write off in taxes, it shows you don't have much to live on or pay a mortgage on. That makes you a risk for an individual owner and a commercial bank.