I'm going to start by saying I have no experience yet as our oven is on it's way. (It actually arrived today at the house, and then the delivery guy said he wasn't equipped to take it off the truck, and then drove away... I'm not even going to tell you how frustrated I am). In any case, with our mobile business starting in about one month, here's what I've planned:
Lighter smaller markets - Two to three folks. One to stretch dough and dress the pizza, one on the oven and handling cash.
Larger busier markets - Three to four folks - One to stretch. One to dress. One to man the oven and cut. One to handle cash.
You don't want the cash person to touch food (otherwise, they have to wash their hands between each time they handle cash and food) so better to stick that person with oven work or just handling cash/orders.
While managing the oven and stretching the dough are the most important pieces for the quality of the pie, stretching the dough is definitely the biggest learning curve... which is likely why I'll be doing that portion when I'm around.
We'll see if my theory pans out, but from what others are sharing here, it sounds about right...