This sounds more or less like a consignment store and pretty much what the amazon marketplace does, but with the work done by a middle man instead. The question is, would people be willing to put up with the higher price or reduced profit required by adding a middleman, or would someone always undercut you because they were willing to go straight to the consumer? It reminds me of all those "ebay shops" that popped up 5 years ago and just as quickly disappeared, though this could be as much about ebay changing their focus as any business pressures, I don't know enough about it to say.

With a consignment store the model works because you are willing to take the reduced profit to not have to put in the actual leg work it would require. People are also willing to pay the slightly higher prices because consignment tends to be in things like clothes that are difficult to buy online.