Buying a house question? Bad credit.

I work full time but I have bad credit. When I say bad, I mean like 530. I'm doing small things to try and raise that the best I can but my medical bills have ruined it. Lol.

I have been paying 600 a month for the past 10 years, steadily, renting apartments and houses. I can pay a mortgage no problem. But banks could care less about rental payment history. I don't have cash to put down really..i guess i could always start saving for it.

What are my options? Also, my fiance has full time employment and his credit is like 570.