Rent to buy could mean a lot of different things - be careful if you are negotiating one of these - the small print can destroy you.
As far as the bad credit, let me suggest you go to Craigs list - and look for private owners advertising there that do not have agents representing them. Agents will advise them on carefully screening. Since private landlords are the most at risk if you don't pay, they should be looking for only the best tenants - but the landlords without agents may be easier for you to convince than those that have agents advising them.
Also, apartment communities sometimes have more flexibility with credit restrictions depending on their occupancy -- that is because they are professionals and one missed payment from you will not typically send them to financial ruin (unlike private landlords who may not be able to pay their mortgage or buy food if you don't pay your rent); PLUS the property managers know their way through the legal system and can efficiently evict you and go after judgement and wage garnishments or other remedies - for them, it's all in a days work - so they can take more risks than a private homeowner.