It depends on what type of work you’re doing and where you live. Some states and industries have strict laws that require business licenses. Check with your local authorities to make sure you’re in compliance before pursuing work.
Generally speaking, you don’t need a business license if you’re performing a traditional side hustle, such as freelance writing or design. However, you may need one if you’re a doctor, lawyer, accountant, insurance agent, real estate agent, engineer, teacher, or public safety worker.