I was flipping through Introduction to Permaculture (2002) by Bill Mollison & Reny Mia Slay and found their motivation for a commonwork business model quite interesting:

For commercial orchards, grain and seed crop, market gardens, and small animal systems (poultry, pigs), small areas of 5 acres or less work better than large acreages devoted to single or even double cropping. It is impossible to completely mulch, water, maintain and raise a large variety of plants and animals for multiple functions and multiple yeilds over a large area (as can be accomplished on a Zone I or Zone II level). Extensive systems, therefore, tend to simplify.

However, this factor can be overcome by a "commonwork" model, where families or groups agree to divide up the work and the products, so that one is responsible for the orchard, while another grows green crop beneath or runs poultry. Someone else might bring bees in during flowering for pollination (and honey production), and manage the firewood crop interplanted with the fruit and nut tree crops.

Smaller systems are usually easily managed by a farm family with seasonal helpers, and provide high yeilds due to mixed cropping and intensive management (pp. 142-143).

Commonwork is often viewed as a way to achieve superior functional stacking. The business is designed to support multiple functions/yeilds with lots of beneficial interactions between these functions/yeilds. The Commonwork model has been very successfully applied to farming by Joel Salatin of Polyface Inc. He runs a dizzying number of businesses under the umbrella of Polyface Inc. Salatin prefers to talk about commonwork in terms of "stacking fiefdoms" and I would encourage you to listen to his Permaculute Voices presentation at this link to learn more (note: Joel is an exceptional speaker and his business ideas are often applicable beyond farming):

Stacking Fiefdoms: Creating Multiple Complementary Businesses Under the Umbrella of an Exisiting Business

Another successful farm enterprise that uses a sort of commonwork model is Freedom Farms. The farm family consists of a large number of brothers with each brother assigned to their own separate but related fiefdoms.

I hope Joel's talk and these examples whet your appetitie to investigate in more detail the commonwork business model. I think a commonwork business model can be structured in different ways but Bill's version of what a commonwork model ideally consists of would be a reference point to compare other versions to.