Cohousing has certain ideas you must have in order to own the name cohousing (at least to some of the founders who want to keep it pure).  One is that there has to be a common house.  I found a post here at a similar type of community called a Pocket Neighborhood where they argue a common house does not a community make.

I like the idea of forming communities in many ways. There are cohousing communities that retrofit a building or a condo or an HOA neighborhood. There are people who link their backyards. There are many ways to form relationships and bump into neighbors.  

Read the article and tell me what you think!