Oh, My God! I Think I've Got Mercedes-Benz Fever!
I've been a good Mopar fan all my life, but watch out. Here's how the M-B Fever starts: first, your son's friends start buying up old Mercedes cheap and fixing them up, and you notice how nicely they are made, and what a quality piece they are (I'm talking about older Mercedes here).
Then your son buys a cherry 1987 420SEL that doesn't run for $500, and you tow it home for him, figure out what is wrong with it and get it running. We're talking about a car that cost $55,000 in 1987. How much would that be today? And if my kid wanted to sell the car, it might be worth $6,000 or so now that it runs well and is smogged. But he doesn't want to sell it. He likes the feeling he gets from cruising around in a luxobarge, if he can just pay for the gas. (Hey, this is a cool car! It has a damn well bulletproof all-alloy 256 C.I. OHC V8 with variable valve timing, 4 valves per cylinder and cross-bolted mains. The stroke is only 3.1 inches, so you'd better believe the thing can rev! Ours has 137K on it, and the compression is excellent.)
Next you discover that this is not an isolated phenomenon: you can almost always buy some really nice M-B cars this way extremely cheaply, especially ones that don't run. In the case of my son's car, for example, when it started to run badly the previous owner bought a new M-B and quit driving the old one. Then the fuel distributor got clogged up from sitting around, and the car wouldn't run at all, so the owner has to sell it cheaply in order to get rid of it.
The trick is knowing how to get replacement parts cheaply. M-B list prices are ridiculous. My son and his friends are good at that.
And then there is the possibility of knowing what M-B parts are in high demand, getting them cheaply at Pick-'n-Pull, and selling them on Ebay. I'm not going to do this myself, but it is a pretty good way for a kid to make money.
It's a whole way of life, I tell you!