Here are some links concerning Portland’s mini-house project.
Their web site http://dignityvillage.org/
You’ll find links here to all aspects, including their incorporation, history, and services. There is also a large photo gallery for the site.
Some news stories:
The MIT dissertation located at http://dusp.mit.edu/sites/dusp.mit.edu/files/attachments/news/mingoya_2015.pdf is one of the most complete resources available.
Catherine Mingoya wrote this for her dissertation in urban planning and examines in depth the mini-houses projects in Madison Wisconsin and Portland Oregon — two very different projects with unique histories and challenges.
While long (89 pages), it offers one of the most complete case studies available online.