Are you asking about a "lease with the option to buy" agreement?
If so, there are a number of risks for the buyer....very few for the seller.
The price will be decided at the beginning of the lease.
The tenant will pay for the "option to buy" the home - that is in the form of a non-refundable deposit either given upfront, or as an amount of rent over and above the normal rent.
The buyer doesn't have to buy, but the seller has to sell.
That's why the buyer would forfeit the deposit - they are paying for that "option" to walk away.
If they cannot buy the home for whatever reason - ie: don't qualify for a loan - they will lose their upfront money.
I won't go into more detail until I am sure I understand your question!
Good luck to you!
Just to further clarify for anyone reading this thread who might be confused by the first response - a "right of first refusal", in which the tenant is offered the house before it is marketed or sold to others is an entirely separate and different option from a true "lease with the option to buy".
It does not obligate the renter to buy and agrees to nothing.