The Business License is evidence only that your tax has been paid. Other permits may be required to open your business.
Every business must at least meet zoning and building requirements to ensure that its business category and site are compatible before signing any leases and moving in. Check with the County Zoning/Planning Department to make sure you locate your business at an address where it is allowed and that it does not heavily impact the neighborhood or require special parking consideration.
Also, if your business name is anything other than your surname or has more than one owner -- a partnership, association, or company -- you may need to file a fictitious business name with the County Clerk's Office, (925) 335-7900. Should you accidentally "infringe" upon another business, you may face legal action and will have to pay to re-file your Business License -- and that gets expensive. So, it is a good idea to do this before you apply for the Business License.
A copy of the fictitious name certification is required with your business license application.