I had an in there around 1999/2000 and was going to end up doing as a part time gig senior year after high school and freshman year of college, but after I talked to a couple people it really it seemed like a tough gig for new people. From what they said at that time it was all seniority based (not that its a bad thing) but basically if you were the new person you'd get the worst selling thing to sell in the worst section and you worked your way up from there. You'd make jack shit in the the first period of time you were there until you got a better product. Selling Frozen Lemonade on a 50 degree day? Sweet!
The system then, as I was told, was that you got your assignment, you gave them up front the cash for what was going to be sold and it was your problem from then on.
I could be completely wrong and got misinformation. I'd love to hear stories from it.