Most stuff can be cooked ahead in one cook for a week and just properly cooled and reheated each day. Ribs are little harder to reheat. But experiment with it or else get up real early to start them.
My new unit is self contained. I vent the FE's thru the roof and can cook all night if I want while sleeping.
Refrigeration is a big dollar item as it all must be NSF approved. Hot holding is another. Last year starting out I used chaffers. I just ordered the 4 well LP steam table and it should be here Wednesday or Thursday.
It's not cheap for a full concession trailer. Mine without the FE's will run about 30K. Add FE's new and it's 40k. The cart and commissary can get pretty expensive as well as you need a building for the commissary. We can't use our own kitchen here in MI. Somebody else here recently converted a garage to a commissary but not sure what it cost.
You probably need to do some more research on both options.
Retired competition cook. BBQ mentor.