Rent to own has a lot of details.
All your rent does not apply to the purchase price. Only the amount over and above the fair market rent. Also, you have no idea what the property is worth at the time of the purchase.
So, you can do this yourself.
Put X amount of dollars away every month, clean your credit and then buy a property. Maybe even the one you rent, but the seller must agree to sell it to you.
So, if they don't want to sell it to you, you will then be in a position to buy another home. The negative to that is that you have to move, but that's it.
Also, a good real estate agent can negotiate for the seller to pay your closing costs or there maybe grants to do that.