Any business with a lax business model, allowing only for the owner(s) to maintain a middle-class or lower lifestyle.
( http://www.urbandictionary.com/define.php?term=subsistence%20business )
The Role of Systemic Adaptability in Subsistence Consumer-Merchant Management of Business and Family
The Divide between Subsistence and Transformational Entrepreneurship
Professor Antoniette Schoar, MIT