I've flipped a few. I had about $40 in a bike I gave away to a friend of my wife. She never rode it but her teenaged daughter likes it. So that was worth it I guess. I got one bike for $10, traded it for a frame I haven't done anything with. I got a Fuji Sports 12 for nothing from an acquaintance and sold it for $20, but then bought the friend breakfast with the proceeds. I got a nice Fuji mixte for nothing from the curb on garbage night, sold it for $50. That was a great bike. A couple weeks ago I flipped a Schwinn Prelude I picked up for $50 earlier this year at a pawn shop, trading it for a Raleigh Super Course I'm riding. Not much profit there for sure, but it's fun.