i had a local scrap yard keep bikes aside for me and I would pay $10 to $20 for each bike, spend an afternoon or so tuning them up to make them roadworthy and then sell them, aiming for a $100 profit. I sold a couple hundred bikes this way over a 5 or 6 year period, using the profits to fund my own bicycle fleet. Profitable and fun, I'd still be doing it but the scrap yard was sold to a condo developer.