Don't know your personal circumstances enough. If you are young, 4 kids, working full time, have unfinished projects around the house, etc. etc., it might be a bad move. But if he is looking for a fun outlet for his energy and we aren't talking tons of money, I say why not. Air cooled VW parts are extremely cheap (it was about 10 years ago but I did a full engine rebuild on one, with all name brand parts, for like $400), and the Karmann Ghias have a following so I doubt it will ever be worth "nothing". Could be a really cheap hobby and unlike some hobbies, you can actually show off what you've done.