The homes cost $125,000 to buy, or up to $1,500 to rent, Patrick Quinton, Dweller's CEO, told Business Insider.
Quinton is also the former executive director of the Portland Development Commission.
For rental units, Dweller buys and installs the homes in backyards, and property managers rent out the units to tenants. The startup then splits the revenues 70-30 with land owners.
The rental price can vary by city, which may also have their own regulations regarding the construction of ADUs.
Like many American cities, Portland is in the midst of an affordable housing crisis. The metro's medium home price is $469,000, and the majority of its existing housing supply consists of single-family homes.
That means older residents who want to downsize may not have too many affordable options. Dweller's homes are a part of the "aging in place" movement, which aims to help people stay in their communities as they grow older.
Cities like New York and Philadelphia have local organizations and officials that are working to retrofit their neighborhoods for aging populations. This can consist of everything from advocating for accessible home construction to building more sidewalks for those who can no longer drive safely.
While it's common for aging parents to live in Dweller's ADUs, Quintin said that he's also seen a lot of interest from young people.
"Portland has a severe shortage of housing — especially rental housing for low- and moderate-income renters," Quinton said. But the city also has "an extensive inventory of single-family properties with backyards ... and plenty of room to add housing."