I don't know if city events, like a chili cook off (I don't know if that is even a huge thing anymore, at least here in Phoenix or places I have lived like virginia or california), would pay you to have this draw attention to their event. Used car dealer lots would probably be the only car dealerships that want this out front simply because the new ones generally want to push the latest models, and not used inventory. Often times, you see them put the top of the line trim package vehicles out at the street, and sometimes lifted newer model trucks/suvs, or tricked out newer modeled cars.
I won't go any further into listing reasons why I don't think it will be successful, because I am not trying to discourage you. It would be interesting to see if you could actually make any good money from doing this. Personally, you would have to pay me at least $500 to be a part of an event using my truck, unless I supported it. I don't know if you are a veteran or not, but one thing to keep in mind is if people found out that you were charging somebody to use your vehicle as an attention grabber, instead of just donating the time/truck, they might not be very appreciative of that. One thing you could do is not charge in an event like that, and try and network as best as you can while you are there, and see if you can line up any future business. Maybe a veteran there has a used car dealership, or a furniture store, or some type of store that usually has some type of attention grabbing icon out front of their property.