According to our resident body man, Salvage titles CAN be converted to Rebuilt titles. Once all the structural work is completed, the car has to be taken to an inspector who will sign off on the integrity of the repairs. There may be a bit more to it than this, but that's it in a nutshell. Once the structural work is signed off, the cosmetics can be completed.
With that said, a rebuilder license is required, which he doesn't have.
He goes to abandoned/repo'd vehicle auctions, and buys cars to repair and sell, but avoids the salvage title cars.
Also... just because a car has a clear title doesn't always mean that it's capable of being made roadworthy. It may cost way more to fix than it's worth, or may require specialized skills. (John was about to bid on a "clear title" Porsche Cayman, until he realized that the structure that was tweaked was aluminum. Way more trouble than he wanted.)