FWIW, I don't think any of the above brokers were BUYER brokers...if Jody means the term as used int he real estate business. Here is wikipedia's definition:"
(or Buyer agency
as it is also known) is the practice of real estate brokers
(and their agents) in the United States and Canada representing a buyer in a real estate transaction rather than, by default, representing the seller either directly or as a sub-agent
. In the United Kingdom
the most common term to describe agent is Buying agent
I personally have never heard of a real BUYER broker in the yacht sale business, doesn't mean there is no such, but none that I have heard of. In a perusal of the public sections of YBAA : Yacht Brokers Association of America
I find no reference to a BUYER broker, the two broker roles outlined in their materials are the selling broker and the co-broker.
Now as a buyer I have used the services of a broker in search of a boat...someone I got to know well and was very knowledgeable. He helped me find a nice boat listed by another broker, and the standard YBAA sales agreement makes it very explicit that the guy I had worked with, was an agent of the seller, and would be paid by the seller.
As I have said before, I think it extremely wise to find and use a capable broker to find the right boat, unless you consider the time, effort and cost for looking at a lot of toad boats before finding a gem part of the fun of boating. I don't think using a broker costs a the buyer anything, it costs the selling broker half the commission..but he expects that, its part of his business model.
As to your last questions. It is very unlikely any seller will let of of a boat without full payment, it would be a legal and financial mess.
You can offer whaterver you want, the trick it you need to know enough about what the boat SHOULD be worth so that you avoid paying more than its worth, if you can pay less than you think it is worth, you should be thrilled. If you pay what you think its worth, then you should be happy you have a new boat at a fair price. I sold my last two boats at my asking prices to the first buyers who looked at them.