When forming your business there could be several different licenses, permits or registrations that you will need to operate legally other than just your Contractors License.
Here is an incredible resource. CalGold.ca.gov. Click on this link and put in your type of business in the box about half way down the page. You'll be asked to narrow down the type of busines then you'll be asked what county you are in and what city you are in. A list of city, county, state and federal web sites will come up.
Review each one carefully to determine what agencies are pertinant to you.