I learned this lesson the hard way as well. Over the past year I've bought about 3-4 bikes I should really have passed on. I only recently got into this hobby, so I chalk it up to inexperience: the rusted-out English 3 speed that was missing its brakes and needed a new wheelset, the other English 3 speed that (like the Cavalier) had been spray painted blue top to bottom, and a Schwinn that was good quality and worthy of getting flipped, but I paid too much for it and didn't make much of a profit. All three have been lessons learned. I ended up donating both of the 3 speeds without putting any new parts into them; the Schwinn I was able to sell, but just barely. It's becoming clear that there are a whole lot of bike flippers where I live; when i check CL I'll often find several groups of ads that are clearly multiple ads posted by flippers. Most of the time, it's just hugely overpriced junk. It's discouraging, especially if I have the itch for a new project.