Hindsight is a huge come-down. I bought and sold guitars and amplifiers on the side to supplement my income in college, and there is very little that I can actually fault myself for, apart for the inability to foretell the future. I traded that Strat for a "Fretless Wonder" LP plus $300 bucks and some other inducements. I traded the LP for two high-end Rickenbackers with MOP inlays, etc. I sold one of the Ricks for every penny of what I had in the both of them and traded the other (a 12-string with shark-fin fret markers) for a really minty blonde Telecaster and a late-60's Princeton Reverb plus an SG standard with a Bigsby Trem. Some of those deals just went on and on. I put in a lot of time and effort getting to know the jazz, blues, rock, country players all around campus and the surrounding towns (and back in my old stomping grounds), and I always had a small dedicated market in mind when a good deal presented itself.
I can't tell you how many Melody-Makers I picked up and flipped for little profit 'way before Joan Jett came along, and made them popular. Also, lots of folks associated Jimmy Page with really potent amps, and didn't realize that when he was recording, he was often pushing the envelope with little amps (like cheap Supros) to get a big sound. Did you know that Clapton and Duane Allman recorded the studio version of the "Layla" album with little Fender Champs? One of the biggest-sounds I ever got on harp was back-miking a tiny tweed Harvard Reverb pointed into a corner of a cellar wall, using a Shure M57 to feed the board, and a really cheap no-name mic to play the harp into.