What is the best way to go about getting real estate financing?

My fiance and I are interested in a home but the home is priced at more than what we are wanting to pay per month. I know if we can get a better interest rate then the payments won’t be as bad.. We have worked really hard on his credit lately (his ex-wife did not get their home out of his name after the divorce, late payments,etc) We refinanced the home after taking her to court and sold it a month later.. I think his credit score is in the mid 600′s maybe low 600′s.. I wonder what his interest rate will be on purchasing a new home? Does anybody have any advice?