In California I needed to post a DBA (ficticious business name) with the county clerk, and get a seller's permit from the state that keeps track of wholesale purchases and retail sales(sales tax).
It is best get separate bank account and start keeping receipts to establish some record of income. You can still do local sales off the books
as long as you stay relatively small and accept cash for payment. The government just wants a piece of the action, but if you report income you can deduct legitimate business expenses.
Good luck
Jeff