Auburn University’s architecture program runs the rural Studio program to design the best possible house for less than $20K. While their structures are larger than the tiny-houses and include both kitchens and bathrooms, they can be a useful resource for efficient space planning. News stories indicate that they have developed many pioneering innovations.
Their goal is to create a home for low income families that would be seen as highly desirable for anyone.
Their main site: (http://www.ruralstudio.org/initiatives/20k-house)
Descriptive news story: http://www.fastcoexist.com/3056129/this-house-costs-just-20000-but-its-nicer-than-yours
Rebuttal to the extreme gushing of the previous story.