Normally buyer will give 1K to seller once he/she signed the OPT and before the 1st Appointment the total amount buyer will give to seller cannot exceed 5K.
so the best case is wait for the OPT to expire and lose 1k, the worst case is 5k. agent can only get commission once the deal has been settled. So both buyer and seller won't lose anything else.
option to purchase gives the buyer right withdraw the option, so to buyer other than money, nothing to lose.
option to purchase secures the seller not withdraw, not deal with others during the OPT period, so if seller withdraw, then it may against law.