Rent to own involves two stages. Renting then creating a purchase agreement. The second part of the owning is an option. It is a state approved form a Realtor would use to create the purchase part.
If you are willing to commit to the guidelines of the option there are sellers out there who are willing to work out a deal but with interest rates at an all time low and fair prices you might not get the most favorable terms.
You will either have to pay above market rent so that a portion of that money is applied towards a down payment or purchase the option upfront with a non refundable down payment. There is a time limit you usually have to abide by and if you don't exercise your option within that time period the excess rent payments or option money is lost.
If you are a high risk consumer the terms will reflect your circumstances. Let me know if this is something that helps. There are always sellers willing to take a risk.