I dabble with them myself. I got good deals on all of them..
The Mercedes is a 1984 190d with 225k miles now. It was $500. Took about $150 in total parts and several weekends of labor. A good interior cleaning, replace the retractable antenna with a cheap fixed antenna, etc. etc.
Runs fairly well.
The BMW is a 1991 318is (manual trans 🙂 ) $900 due to a BAD oil leak--took a while to find it as the oil was leaking from one place and would drain down some hidden areas to make it look like it was coming from somewhere else. A bit of other stuff (broken bolt on the valve cover, new ball joint, new tires). Total parts about $400 (tires were the most expensive), and several weekends of labor. Runs quite well--a fun little car to drive. I was not a huge BMW fan until I got a 1987 325e (the 'efficiency' rather than the sport version), and it handled quite well. Then I got this one--quicker with better handling. I even found a better deal for my Brother--$300 for a 1987 325es (2 dr. manual) that only needed minor repairs, and was in nice cosmetic shape. He's playing with that one now.
The Porsche is a 1984 928S (auto trans 🙁 ) A bit more expensive at $2k. Didn't run when I got it (74k miles)--turns out the ground wire for the fuel pump had corroded and was not making good contact. There are a fair # of other issues--leaks from the sunroof and hatch had cause interior problems, headlight motor didn't work, passenger window motor, sunroof cable is frozen, rear seats completely gone (the leaks dried the leather up), needs the rear hatch lock re-keyed (the reason for the leaks--it didn't close entirely), the carpet replaced, and a few other items. Just barely getting started on it (got it running first). Unfortunately, I don't have a garage here, so I'm limited due to the weather. This car will take a couple of months to get in reasonable interior shape (it will never be a show car), but I have all the parts--about $600 total including $200 replacement front seats, and replacement tires ($150 for a set that were only used 1k miles). Just going to take a fair amount of labor, but even at 240hp, it moves VERY well when I punch on the gas, and it was one of the fastest production cars in the year it was made.
So, I play with the cars. The boat was a whim (sold a Motorcycle I was fixing to pay for it)--it is a 1954 Owens Speedship. Should be a fun little toy when I get it cleaned up and a rub-rail replaced on the outside.