Mobile Catering Unit or Gazebo

I am looking to set up a mobile catering unit to supply events and festivals etc.

I cannot decide whether to buy a trailer and do it all from there, or whether to do the food at ground level under a gazebo (which I would prefer).

I need a griddle, bain marie, water heater etc. I would also need some kind of fridge - one for drinks and another for uncooked meat and veg products.

I would prefer to use a gazebo but I am worried then how to pass this through hygiene standards as I would not have a 'premises'. I also wonder if I have to have a sink and running water.

Also, can you tell me the practicalities of using a gazebo over a trailer?

Many thanks.