All the people I know do it on the lamb. They walk around the parking lots and the main traffic streams and sell their shirts out of a gym bag. WARNING! If you get caught, you will usually get fined. Usually anywhere from a few hundered to a thousand bucks.
Usually the concert or event promoter is not going to let you vend, as they're already tied into the merchandising action. Most venues will not let you vend on their property becasue of the agreement w/ the promoter or event. The bigger the event, the harder it is to be a legit vendor.
Some towns will allow you to get a vendor permit, but you'll probably have to stay off the venues property. Plus it usually has restrictions to where you can vend.
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