The simplest business structure is the sole proprietorship. Simply put, your business is a sole proprietorship if you don’t create a separate legal entity for it.
This is true whether you operate it in your own name, or under a trade name. If it isn’t your own name, then you register a company name as a “Fictitious business name,” also called a DBA (“Doing Business As”).
Depending on your state, you can usually obtain this through the county government, and the cost is no more than a small registration fee plus a required newspaper ad, for a total of less than $100 in most states.