I used to work for a ticket company (a junior version of TicketMaster) and it is legal in my state to resell theatre/concert tickets at a higher price than you bought them (AKA 'scalping') but not for sporting events. You should check with your state and local laws before getting into this. The secret that these people had? They had a 'VIP' membership to the local theatre (local being a huge theatre, all the big shows came through) and could get very good seats to sold-out shows, then would resell them. The main person doing this shot themselves in the foot, because he put a scanned copy of his ticket on the auction, so we could track him down by the seat/row/night.