With $4,000 down there are several different financing options that actually allows you to purchase/own a home.
I strongly discourage a "Rent-to-Own" solution for owning a home. I suggest talking w/ a lender to determine why you can't purchase now and how long it would take to repair your credit. Once you know the amount of time you'll need, I suggest finding a home willing to do a "Lease Purchase." This way you lease the home during the time you're repairing your credit and then you'd purchase it when your credit has been repaired.
Rent-to-own options prevent you from technically "owning" the property, meaning your name will not be on the deed of the property. This completely eliminates the possibility for you to build equity in the home. In the long-run it will be much cheaper for you to own it (via mortgage) instead of rent it. Don't throw your money down the drain.
Feel free to contact me if I can ever be of assistance. 337-884-4843 or firstname.lastname@example.org