The Census Bureau calls these businesses nonemployer firms.

According to data for 2007 (the most recent available):

Real Estate Appraisers: 19%
Software Publishers: 14%
Bed and Breakfast Inns: 8%
Carpet and Upholstery Cleaning Services: 8%

Nail Salons: 16%
Landscape Architectural Services: 15%
Clothing Accessories Stores: 13%
Confectionery and Nut Stores: 6%

Most of the money earned by nonemployer firms comes from, in order of size:

  • Real Estate Services,
  • Professional, Scientific and Technical Services, and
  • Construction.

They are often part-time ventures with owners operating more than one business at a time. The most recent recession has hit the real estate market and construction industry particularly hard so this data may change.