[sailingfool]

Hundreds of boats get sold every Winter and all such sales deal with these considerations, and most of them, especially those that work out successfully for the buyer follow a set of conventions that the experience of hundreds of sales have established.
You can negotiate anything, but if you don''t have the experience to know when to hold versus when to fold, you''re more likely to get yourself into trouble than to avoid it.
My opinion - develop trust with an experienced local broker, and work your purchase through that person, regardless of where the boat is located - who will get a piece of the commission as comp. If you don''t want to take that approach, look for a lawyer who has handled boat sales and pay for assistance.
Otherwise you''ll pay for your mistakes as you learn the right answers to your questions, and your cost exposure is fairly open-ended.