I would guess given the comments on these posting there are lots of way to do this however most often (especially if dealing with a broker) the purchaser makes a bid and can (should) make it contingent upon a "acceptable" survey. A good will 10% deposit is almost always turned over in escrow to the broker at that time.The offered price is negotiable after the survey to compensate for any defect found. If an "unacceptable " survey is found the purchaser also has the right to "cancel" the deal. Most times the offer can be withdrawn based on mechanical or structural repairs needed especially if the owner is not willing to fix them. Because you changed your mind or found another boat is not an acceptable reason. If the survey is acceptable the deal is good and goes to the actual purchase of the boat. This process is very similar to real estate and a home inspection.
In today economic time I guess anything would go as long as the purchaser and owner can work it out so basically there are no rules. There are advantages to a broker being involved especially as the cost of the boat become higher so does the risk. I suppose you might find an owner who will let your survey his boat then make an offer but the owner has no obligation to accept your offer and now you have paid for a survey. As an owner I would insist upon seeing any survey performed on my boat before I acknowledged any defects. Suppose the boat passed survey 100% and now the owner wants top dollar? A good survey is a sellers advantage and a poor survey is a buyers advantage when negotiating price. That is why almost always the price is worked out before the survey. Also be warned that even with a survey showing defects the owner can still refuse to repair the boat or make a monetary adjustment and you then either have to accept the boat as is or walk away from it. As with any purchase always remember "buyer beware"
