If you will be using a fictitious name for your business (a name other than your personal legal name), you will need to check with the County Clerk to be sure no one else is using that name . You will need to file a Fictitious Business Name Statement within 40 days of the business start date.
$40 fee plus $9 for each additional owner/business name, (plus cost of publishing statement in adjudicated newspaper). (If no changes, good for 5 years.) (As of June 2016 - for current info see Fictitious Business Name Information.)
Statement must be published once a week for four consecutive weeks in an adjudicated Sonoma County newspaper (first publication must begin within 30 days of when statement was filed).