Rent to owns are rare and even more rarely are they a good deal for the renter/buyer. The vast majority of rent to own renter/buyer's never end up buying the house. They are a great deal for the landlord/Seller as they get to collect large up front deposits and over market rent only to do it all over again in the same house. I consider it basically immoral and predatory in most cases.
Resolving credit issues isn't rocket science and a local mortgage lender can and often do assist buyers with this. Many things you can do yourself, others the lender can direct or assist you with.
Most people in this position are far better off renting the least expensive place they can stand to live in and save up some down payment, get on a budget and fix their credit. Once you are qualified, you can select any listed property in your price range and you've fixed the issues that hurt your credit.