You are on your own. You don't have a boss. You don't have any partners. You don't have shareholders. You're a sole proprietor.
Sole proprietorship happens.
It happens without taking any particular action on your part. It happens when you hang out your shingle, when you collect your first fee, when you write your first check on the business. A sole proprietorship is you . . . You don't even need a separate bank account. But it's a good idea because of taxes.