This was the best site I found when I was looking for a boat:

http://www.boats.com/listing/cache/advanced_search.jsp

Here's how the broker thing is supposed to work:

The broker, representing the seller tells you whatever they think is
in their best interests for you to know. If the keel is missing, it
isn't in their interests to take time for you to show up and discover
that. OTOH they are under no obligation to tell you that there is
core rot.

You make an offer based on the information provided and, if possible,
your initial look yourself.

You hire a surveyor. If you are smart, you'll pay to have one travel
from outside the area. The local guys get referrals and work by
making sales happen. Be there for the survey yourself. You'll learn
a lot more than from a report.

The cost of fixing anything not previously disclosed, clearly visible
in the pictures, or on your initial inspection is then deducted from
your offer. Each party then decides if they want to proceed. If not,
you get your deposit back. If the keel was missing in the photos or
on your first inspection, that would not be deducted from the offer
because you should have factored it in at the time you made it. If
the surveyor finds core rot that was not disclosed, that would be
deducted because it could only be discovered by the survey.

It is true that surveyors are just normal people and not psychics so
there will inevitably be lots wrong discovered after you own the boat.
That's just life.

Buy in the Great Lakes (or other fresh water) if you possibly can.
Not only is there and incredible difference all the way through a boat
that has not been heavily exposed to salt there are different broker
practices, at least in the Detroit area. Our boat came with a $2000
escrow to cover anything that could not be discovered by survey. Any
system thing that didn't work. Because we got such a low price to
begin with, I didn't hold their feet to the fire for the autopilot and
stereo that I didn't really care about but they ended up spending
nearly the whole amount on fuel system problems that we would have
been stuck with under typical arrangements here on the east coast
..
The fresh water factor even shows up in the woodwork. Salt gets
everywhere and the residue holds moisture. I've seen five year old
boats that were not as fresh and clean in out of the way corners as
our 1980.

--

Roger Long