dg, if you hunt around there are many older threads on the perennial question of whether an old boat is a treasure trove or a hole in the water. If you don't know boats, and don't know someone (who you'd trust intimately) who knows about boats, you want to hire a surveyor.
If the NASA "employee" is the guy who messed up the o-rings on the shuttle, you don't want the boat. If he's a cafeteria clerk, harder to say. If he's an obsevvie engineer who kept maintenance logs and receipts, that's better prospects for a good boat.
The problem is that if you don't know boats, you have no idea how expensive a rotted deck can be, or "just a waterstain" on the bulkhead, or a little corrosion on the chainplates, or a couple of bad keel bolts. How bad? Well, you can sink $20,000 into a $5,000 bargain boat that could have been bought outright for $15,000. And you can't just walk away from a bad boat--you've got a rather large disposal fee to get it hauled away and scrapped.
It's a funny thing, but aside from the few almost mythological deals ("The divorce says I have to sell the boat and split it, but I want to screw my ex so I'm selling it for ten cents on the dollar") it is still most likely that if a stranger is selling you a boat for $5,000, the boat MIGHT be worth what they are asking for it. But if it was worth four times as much--they'd have no trouble selling it for $20,000.