I use a broker for a couple of reasons. These guys are professional boat shoppers and can usually find deals not available to the average Joe who doesn't have time to search yards, peek under tarps etc. If you can find one you can trust (rair as hens teeth) they should be looking out for your interest. A broker should know the market and as such he/she should let you know if the boat is a good or bad investment or just a fair deal on a good boat.
My broker does business on both coasts but has just moved permanently to MD. He has been in the business for 30+ years and is a performance boat sailer. If interested send me a PM and I can give you his contact info.