First and foremost, contact your local Health Department for your county to understand what sort of requirements they have for your commissary and/or onsite preparation. Next, your local city for business licenses, and then the State for sales and tax issues. Then insurance for vehicles and general liability.
There are at least a hundred other things to know in order to be safe, legal, and in business. Take your time - Research, plan, and do things right the first time an you'll stand a good chance of getting off the ground.
Rancho To Go BBQ Catering
Spicewine BBQs - West (Left) Coast
Large Spicewine - Ol' Blue
Twitter - @ranchoagogo @ranchotogobbq