Vendors can draw a solid salary
While stadium beer sales statistics are harder to find than a sensible explanation of VORP, there's some scratch math you can do to figure out a beer seller's salary or at least be... in the ballpark. If a vendor works every home game, and can move an average of 10 cases of beer per game (240 beers), on $.50 tips alone (there’s also a commission on each beer), they can draw a five-figure salary in a season.
You might be getting served by a middle school history teacher
Thanks to the part-time flexibility, beer vending is a second job for most. Among the staff you'll find school teachers, constructions workers, etc. Rocco, himself, was even a mail carrier at one point.