T.
I am a realtor and am currently in this situation on my own home. The actual lease needs to be drawn up by an attorney as each situation is different. Some leases are just strictly leases until they are able to purchase the home, some leases provide for a certain amount to be held in escrow each month to cover closing costs or down payment (typically an amount above the mortgage payment). I am typically a bit more wary of owners that will owner finance and do a lease to buy situation. These situations are entirely in the owners favor and many will provide for no flexibility. If you need help in finding something let me know!