B.K.
Depending on the festival, he might need a permit from the festival organizers, and also a permit from the county department of health. He also may need to be inspected prior to opening his stand. (At our local July 4th festival, the inspector shows up at a given time and inspects everybody before allowing the food area to open.
He will need enclosed containers for food items (i.e. rubbermaid bins) soap, plastic gloves, buckets for holding water to clean things, extension cords, plastic racks to keep things off the ground and thermometers to make sure the food is cooked to the proper temperature and the things on ice are cold enough...... and then all the things Nicole mentioned.