Tickets, whether they're for political rallies or rock concerts, are a valuable commodity. And like any other commodity there are people who make a living buying and selling them, acting as a middle man for popular events. However, it's important that people and businesses that choose to do this follow all of the laws and regulations regarding ticket sales, reporting and various other, important rules.
There are literally dozens of ways to get ones hands on tickets to events. Business persons could buy them from the box office on opening day, work out a deal with event or venue coordinators, or any of a dozen other methods. However, which tickets get bought for which event is an important decision that people have to make. Events that aren't popular, after all, won't yield very big results when it comes to ticket sales.
has them, tickets can be sold in a variety of different venues. For instance, selling tickets outside the venue for sold out shows is one option, but it is a very shady one. More often people who do serious business in ticket sales tend to operate in store fronts, or to set up websites for ticket purchase. Thanks to technology it's entirely possible for someone to go to a website, transfer money and get a ticket emailed to them all on a smartphone, making getting into the events they want a much easier endeavor.
If the seller can't get the tickets for less than the box office is charging, then the price of sale will have to go up. The only way to get ahead doing this is to have tickets to very popular, sold out shows where people can't just buy tickets at the door for a lower price than you're currently asking for.