Lamonica, yes, you should absolutely focus on cleaning up your credit first. Whether you decide to commit to a rent to own or simply purchase a new home, landlords/owners and lenders will be reviewing your credit history to reach their decision.
In many cases that is the precise reason that people do a rent to own in the first place. Most landlords understand that there are some credit issues, otherwise you would be able to get a mortgage. I personally wouldn't carry a note for 30 yrs but I definitely would for say 3-5 yrs. Then hopefully your credit score is repaired and you could get that mortgage for a price agreed upon at the beginning of the lease.
You may find sellers who are willing to do a lease purchase or option to purchase with you. If you have credit issues with not paying for you current living space - then it will be more difficult for you to find someone willing to take the risk. It will be important to ensure you don't overextend yourself and can afford the payments to make this successful. There are a number of folks who get into this situation and can't afford the rent payments or can't qualify for the home and they end up without the house anyway. There are many risks - so make sure you understand what you're getting into before signing any contracts.
It's always a good idea to clean up your credit, because if you eventually want to purchase the home and obtain a FHA, VA or Conventional loan - this is criticial! There are some sellers who will do seller financing, but they'll typically want a good down payment to assume the risk.
There's lots of info out on the internet to help you .. the first step would be to get your credit report. I'd recommend that you work with a good mortgage broker who you trust. They can pull your credit for you and many will even work with you to make a plan on how to improve your credit and give you a realistic figure for what you might qualify for and how long it will take. Here's a few links on how to clean up credit: