This subject has come up between a few friends for years because some of us participate by cooking at various events during the year. We have fun, and it's very enjoyable to hear "thank you" or "this is great barbecue" 300 times in one day. One reason I never even wrote out a catering or food truck business plan is that most events are on weekends and Friday would likely be prep day. Being an owner and having employees is an option, but it's taken me years to wind my company down, cheery pick customers, and be in semi-retirement.
I'm assuming you would open a "for profit" business, selling some of your food to the public? The best starting place is your city or county health department. They should have printed information for catering or a food truck and include all the rules and regulations.
If you are not opening a "for profit" business, there may be some loopholes. For example, my state has a law called the Traditional Food Act and below are some snips from that Act. So, lets say someone wants me to cook for a wedding rehearsal and feed 75 people. If the father of the groom pays for the food, and I help out with the cooking, and guests are not charged.... there are no permits, licenses, inspections etc. There are some local people that have rental equipment, like a trailer sized grill or a hog cooker, tents, tables and chairs and the like which generate their income for the day, it just doesn't come from selling food.
Notwithstanding any other provisions of law, there shall be no license, permitting, certification, inspection, packaging or
labeling required by any state governmental agency or any agency
of any political subdivision of the state which pertains to the
preparation, serving, use, consumption or storage of foods at a
traditional event or activity.
(A) For family and nonpaying guests;
(B) For weddings, funerals, potluck dinners, charitable
dinners and charitable cook-offs or functions as defined in W.S.
35-7-110(a)(xxix);
(C) For the sales of donated foods which are prepared
for consumption and the sales are sponsored by a nonprofit
entity as a fundraiser to support its purposes;
(D) For outdoor activities such as picnics, barbeques,
roundups, camping or outdoor work conducted by employees or
volunteers;
(E) By utilizing kitchen equipment provided by employers
as a convenience for the storage and preparation of foods for
consumption on the premises by employees and nonpaying guests.