Having gone through this process a two years ago:
Things that entered my mine were:
- Boat Type/Make - How Available
- Boat Age
- Boat Condition - Overall
- If not showroom (nothing is) - Cosmetic or Major "repairs"
- Is price "fair" for condition - compared to other similar boats
- What is my budget (with "fixes")
- Do I want want to accept a boat knowing it has "major" repairs knowing that I would have to fix or pay to have fixed.
I agree with a lot of the advice that others have suggested, but Kwaltersmi's is pretty much the cap note to all the advice. In the end you have to be comfortable with you offer/price. If you think it is worth a million dollars to you, then it is.
I bought a house 10 years ago and my neighbor came over a few weeks later and said that the Previous Owners offered them the house for about 30K less than what we spent. They thought it was too much, which was kind of a backhanded way saying they thought we were screwed. 6 months later a similar house across the street sold for $200K over what we paid, albeit in a bit more showroom condition than ours was when we bought it. My neighbor came over and said looks like we got a pretty good deal.
When I bought my boat, Pearson 10M, I looked at a lot of similar boats. The 10M is a lesser known Pearson model compared to others, so for some reason it doesn't command a as much of a "premium" price. A Pearson 33-2, and Pearson 34, albeit 3 to 5 years younger, were asking 12 to 20K more that what I bought my boat for.
As far as were to start the negotiation, pick your absolute max price that you would pay for the the specific boat that you are looking at and offer 70 to 80%. So say the boat is offered at $20K. You think it worth, $18K because of the factors listed about. Your willing to pay $18K max, so offer $14.5K as a start, If the owner comes back as says $17K, then you have to determine to you want to keep negotiating or take it as that number is below your max. If the owner comes back at $19K, well that tells you something too. Maybe time to move on, put in a counter offer say at $17K, or reevaluate how much you want this boat.
Again, in the end, you have to be comfortable with your price.