Karen, This will bring you an avalanche of
responces. I would look for signs of abuse beyond normal wear and tear. They are pretty obvious. Knocks on the woodwork ,chips and cigarette burns, spills that weren't cleaned up. Engines in that age could be diesel or gasoline either is acceptable if it has been well cared for. Perhaps the best sign of a well cared for engine is cleanliness. If the owner kept it wiped clean and painted the rust, if the insulation on the wire is clean and the connections are not showing signs of corrosion and there are no empty oil bottles lying about, it should be better than fair. Check the underside of the cushions for mildew, open all of the compartments and use your nose, the boat should have a neutral smell. Don't be too influenced by "sleeps 6", can it toilet four. if you cook check out the galley to see if you could make meals there when the boat is moving. There is much more and others will add much.