Oregon and particularly Portland have been testing grounds for Tiny Houses, cleverly constructed homes with 400 sq ft or less. Some Millennials are interested because they can't afford a normal home. Homeless advocates think they could be an alternative to cardboard boxes and bridge overpasses. Some people just think they're cool or need a place for granny to hang out close by. But building and fire codes can be a barrier.
Here's an article with links to the legislation that is greasing their wheels.