The thing to remember With Rent To Own is you'll be locked in both to the house and to the price, even if it takes you 3 years (or more?) to save enough for the down payment through the forced savings of the rent payments. What happens if three years from now your life situation has changed? Maybe you need a bigger/smaller home. Maybe your employment has relocated. Maybe your credit or income is insufficient to qualify for a mortgage loan.
Find a way to save up on your own; not with Rent To Own.
Sit down with a local Mortgage Banker and get yourself prequalified, too. You may find you're better qualified than you think you are, and, if you're not, at least you'll know how much loan your income and credit qualify you for, and how much you have to save towards down payment and closing costs.
If you do go with a Rent to Own option, be sure your attorney explains the contract to you THOROUGHLY, and assume it is usually going to be a better deal for the seller than it is for the renter/potential buyer.