I've done this event before and had trouble getting paid. I was assured that if I turned in an invoice and got a purchase order, I would be paid the day of the BBQ. I showed up ready to cook onsite--they were not prepared to hand me a check---I left. If I had not explained 3 months prior to this event what I expected then I might have stayed and cooked. I was very clear that the "Getting Paid" problem needed to be addressed. Last year I told them the same thing and they gave me a credit card to bill. In 2007 it took 120 days before I was paid.
I have never "not cooked" an event that I was scheduled to do until now.