At the prices I buy at, I don't consider my purchases risky, nor do I think there is much criminal profit to resell dodgy bikes. When I collect something covered with dirt and cobwebs with flat tyres and old lights full of leaky dead batteries in them, I know those bikes have been stored for years and not taken off the street. That said, I still wouldn't knowingly buy a bent one, and I have passed up the odd one because I didn't like something about the seller's wares for sale or their past feedback etc. I don't get too hung up on receipts and paper trails. If you are buying stuff that is 25 or 30+ years old, you are unlikely to be handed the original bill of sale and the owners handbook - even from the original buyer. I've got just one documented bike, from 1989. A lot can happen in those years; people move address, receipts get chucked out, bikes may change hands several times - and the more they slide into cheap hack territory, the less importance is placed on provenance.
