I am not an attorney, and I think you should ask one to be 100% sure on this. However, I will tell you that if you are considering a lease with an option to buy, it depends on how you set it up at the beginning. Typically yes, after a 1-3 yr period, the option money initially given to you and the additional amount paid each month over and above the rent amount goes towards building the "equity" in the home so that they should be able to go and qualify for a conventional financing, at which time you would be paid in full.
In addition to consulting an attorney, you should also consult a tax advisor to determine if this would be in your best interests. Good luck with it!