Established food places for sale??

Not quite sure that is the best title.
I recently read a post that suggested to someone to try to buy a mobile food deal that was for sale. The thinking behind is that they would have a spot in the local fairs/events and that it is hard to get into.

So... can you give some ideas on where to look for mobile food places for sale??

Also, just as a quick update, I have my next event in 8 days, I am hoping that it goes much better than the last one. With gas prices so high, I am a bit worried about the turnout!!!

I will let you know how it goes.