Take the boat for a ride before you buy

Check engine oil and make sure there is no water mixed with the oil, check dipstick to see if oil smells like it is burnt. Check outdrive oil for metal shavings there should be some but not large amounts on the plug. Make sure there are no leaks in the transcom.

the engine is what you want to work the best provide the hull doesn't have any major leaks in it. If it has carpet in it pull the carpet up and check the wood/fiberglass underneath for soft spots, see if you can tell if the stringers have soft spots in them, if they do this means they are water logged. if that would be the case stay away from it. Check batteries, horn, lights, blower, bigle pump to make sure they all work. Fittings on fuel tank. Find out if the company that built the boat is still around and can you get replacement parts for it. this sounds like a private sale, there is no recourse afterward, if you go to a dealer usually there is some recourse if the boat dies on you. good luck with your venture.