If I may, a suggestion from a cruiser that used to be a yacht broker. Depending on the boat you're looking for you might only need one. Any broker can sell you any boat listed for sale
with any other broker, even if it's located in another state or the other side of the country. One good broker can do a lot of the leg work for you and narrow down the search. Note the qualifier one "good" broker. Unfortunately there's a lot of brokers that don't put much effort into the job and even a few that are downright scoundrels.
If you aren't buying
a really expensive boat it might be good to look for a different broker in each area you plan to search. Wouldn't make much sense for a broker in Annapolis to travel 1000 miles to Florida
to sell you a $20,000 boat. On the other hand, if you're planning on a million dollar deal you might find a broker that will travel across the country for you.