independence has nothing to do with this. As a minor, he can't legally enter into any contractual obligations with a business or person. Oral contracts, written, etc, all are null and void because he is not an adult. He has virtually no rights whatsoever in this scenario, and he's lucky the dude is shipping his mobo back. The reason why adult supervision and involvement for minors attempting to engage in business transactions online is so vital is for situations just like this. An adult would have (hopefully) had the foresight and life skills/experience to judge that this was an inherently bad idea and that in the event legal recourse was necessary, rights would be preserved.
This is how kids get into trouble these days. Meeting strangers, talking to strangers, giving them their address, winding up on To Catch A Predator and Nancy Grace. Parents need to monitor their children's activities and interactions online. Internet safety isn't just physical, it's financial as well.