My view on buying dubious boats... assume it will need new engine/drive. Actually engine/drive issues often the cheapest and easiest things to fix on a boat, i.e., you pays your money, you get "new". Now hull issues are a totally different thing. We're talking, transom, stringer, decks as these impact safety.... ugly gelcoat...not so much. IMHO, these types of fixes are more risky than an engine/drive fix. There is no such equivalent as "buy new" ( and bolt in/on) fix. You are always at the mercy of a practitioner's skill and temperament, more so than with the mechanicals, and DIY fiberglass work is harder to learn to do acceptably than much mechanical work. Mess up a fiberglass job and it's not an unbolt/buy another/redo fix.
That said... I'm a great fan of classic boats. There are some nice "collectable" ones out there. Bertram, Hatteras, some Chris Crafts, and a number of smaller ones that hold their value well and are worth becoming "project" boats. Some "big name" ones are nightmares.
With few exceptions, time and money you put into fixing up a boat is sunk money (although some folks are making a business out of restoring and selling restored vintage Bertrams and Hatteras... and the odd restored Chriscrafts sometimes sell for big money).