tiny houser
n. A person who lives in a very small house, or who is an enthusiast of very small houses.
Also Seen As
Johnston's "Meetup" group currently consists of 180 "tiny housers." They get together once a month to talk about where and how to build, how to educate others and how to advocate with government and community stakeholders.
—Josh Green, “Advocate: Atlanta's Tiny House Movement is 'Growing Fast',” Curbed, February 24, 2015
The 11-acre campground along Highway 198, just before the village of Lemon Cove, is nestled into the rolling hills and shaded by small olive trees. There are 55 sites with more than half having electric and water hookups. The other half of the sites are for tiny housers who want to live off the grid.
—Bonhia Lee, “Home sweet tiny home: Valley houses fill less than 300 square feet,” The Fresno Bee, December 21, 2014
I know people in three different boroughs who make do with an embarrassing paucity of square footage. But he and his fellow tiny housers are taking space-saving to an entirely different level. As the documentary opens, Smith marks up his notepad with plans to hand-build a 124-square-foot structure. Later on, a woman shows off her 98-square-foot home. Tammy Strobel and Logan Smith live together in a tiny house, a happy couple inhabiting a mere 128 feet of real estate in Portland, Ore.
—Neil Drumming, “Tiny houses: Cute, environmentally friendly and sometimes illegal,” Salon, November 13, 2013
2008 (earliest)
On Sunday, I continued north to New Hampshire to the residence of another tiny-houser. …As all his appliances are spread to other buildings, the house is a small (about 100 square feet) free-standing room with shed roof, with room enough for a futon, single bed, desk, and heater.
—Amanda, “Small Presences,” Closer to Home, September 23, 2008
Many thanks to Amy Plourde for suggesting this term. Also, if you find tiny houses irresistibly cute, be sure to check out Tumblr's collection of posts tagged #tiny-house.

A tiny house in Portland, Oregon. Source: Tammy Strobel via Wikipedia [CC BY 2.0].