The homeowner gets the petite outbuilding free in exchange for an agreement to serve as a landlord for an otherwise homeless family for 5 years. After 5 years, the homeowner gets a tiny house that's been lived in for 5 years and they can do what they want with it.
The living quarters, to be used in your — or your neighbors' — backyard, "would be about 200 square feet, with bunkbeds for the kids and water, sanitation and plumbing."
What sort of homeowner would do this? You would have people — with children — living right next to you in a horribly cramped space and you would be the landlord, with the responsibility to maintain habitable conditions. But you are not an experienced landlord. You may have good intentions and think kindly of the homeless in the abstract, but how would that idealism translate into proximity to real people who are your tenants, whose problems with the living conditions are your problems. Do you think these people will love you, their benefactor? You are the landlord!
But maybe you're thinking: If I can deal with this for 5 years, I'll be able to AirBnB it....
(Rethinking buying a house in Portland.)