Not exactly the type of story you are necessarily looking for, but makes me thinks of something I did at 14 back in 2004.
I was mowing lawns to make $$$ then and had a family member take me to look at a commercial mower that was listed in the local paper (don't think the section in the paper even exists today lol). I bought it for $700 (had to do a few minor maintenance things like changing the oil, filters, plugs, etc.) and used it for a few months, then found Craigslist shortly thereafter and after some Googling decided to try listing it on Craigslist for a much higher price than I bought it for, $1,700. The next day, I got an email from a guy that mowed for a living saying he only uses these specific machines because of their controls (called "T-Bars"), he showed up, offered me $1,500, I negotiated him up to $1,600. I remember recounting the $100 bills thinking I had hit the lottery!