How can one sell music related photogrpahs from gigs etc?

I would check with the bands. some bands have what’s called copyrights which prevents anyone who tries to sell pictures illegally without the band’s consent. then there’s the venues where you took the pictures from. they might be interested if they’re good and might buy pictures from you. magazines might be a bit harder since they might not buy from people who aren’t professional photographers. or pay for good pictures but would offer to put your name in as credit. if you do want to try to sell pictures to a magazine try something like a teen magazine or guitar music magazine. People or rolling stone might not buy but it’s worth a shot.
good luck.