You may get your license at the local Health Department. You have to apply first before you obtain the permit to operate a business catering service. An inspection will be needed to check if you will pass the food sanitation requirements. After you have acquired your license, there will be regular check-up routines to ensure that you will sustain cleanliness and sanitation of your catering service.
There are states that require a catering service must have a separate area for the food operation and the kitchen facility of the house. This is important because they will not issue a license if you have a set up wherein they may see food sanitation is not your priority. If you want to remodel the set up, you must pass the plans and remodeled features to the Health Department for confirmation that you are following the required construction to your home facilities and to your food operation area.
It is important to target your market in this business if you are given the permit to operate already. Know your competition and be aware of their strengths and weaknesses. If you are stable with your finances, you may hire applicants that are experienced in this kind of business.