A sole proprietorship is the simplest form of business. Although not considered a separate legal entity, by default, once you start operating a small business (i.e. selling goods or services) you become a sole proprietorship. In a sole proprietorship, there is no separation between the business and individual owner.
Even with low start-up costs and ease of operation, factors such as unlimited liability for all business debts and liabilities can make a sole proprietorship the most expensive type of structure in the long run.
As a sole proprietor, if you intend to do business under a name other than your legal name, you will need to file a DBA