Ron brings up a lot of good points. A Rent To Own (RTO) is simply a home that the owner will give you an option to buy while you rent it, usually by paying a little extra each month in what can be either a purchase deposit, option fee, or both. A specific option expiration date is usually identified. If you don't exercise (buy) the home by that date, you lose the option and any fees or deposits that you have made. That said, the actual terms on any RTO are not pre-defined they can be whatever you and the seller agree on.
In the RTO sales that I've brokered, the seller ALWAYS required that the renter/buyer have good credit from the very beginning. Whether the seller would give you the loan to buy his house or you have to go to a regular lender for a mortgage, good credit is always required.
That said, there are some RTO sellers will allow a renter/buyer to start the process because they know this fact: Very few RTO sales that start ever actually end in a sale. Either the buyer decides they don't want the house, the buyer decides they can't afford the house, or the buyer can't get financing before the option expires. Some sellers will accept the RTO buyer as a renter and take their rent, option fee and deposit knowing that it's all profit for them - until the deal falls apart. You don't want to work with that type of seller.
Best of luck.