Lease purchase options are complicated and not a win-win solution. Reportedly, only 10% of lease purchases result in the home getting sold so a seller needs a large non-refundable deposit to cover the cost of putting the house on the market again (for example, repainting and new carpeting) after the tenant leaves. If the buyer pays the large non-refundable deposit and then decides not to buy the house, they lose that deposit money which they wouldn't have had to pay had they selected a normal rental. Also the seller usually requires that the buyer pay more than a comparable rental price with the extra money going toward a down payment.-- more money that a buyer loses if he doesn't purchase.
If the house isn't in move-in condition, the owner may not have much to lose in renting it, so he may not ask for a large deposit which would make it more economically practical to the buyer, but would that be a house you want to buy?
If you pay a deposit, you have to worry about the seller declaring bankruptcy or letting the house go into foreclosure while you are staying there, in which case you probably won't get the deposit back and may not be able to purchase the house. You can overcome this problem by having an attorney act as trustee and hold the deposit money. You definitely need an attorney to write the lease purchase agreement so that you are protected.
If I were advising a seller, I would ask why they think that a buyer who doesn't have good enough credit now is likely to be any better in 6 months or a year. If the seller wants to sell, they are just delaying the sell date and will have to prepare the house again to put it on the market.
I would generally advise against lease-options,