A startup is building $125,000 backyard 'granny flats' that can be constructed in less than a month

For a long time, moving to nursing homes or condo communities for people ages 65 and over were some of the only options for those who are aging. Living in single-family homes - especially if they have more than one level or are too large to clean easily - can be difficult for people as they grow older.

A growing number of cities are now beginning to think differently about how people can instead age in place, retrofitting neighborhoods to accommodate aging baby boomers.

One approach is the Accessory Dwelling Unit (ADU), which is also sometimes called a "granny flat" or "in-law unit." The small homes are designed to go in backyards, so that aging parents can have independence and the option to live near their adult children.

A new startup, called Dweller, designs and builds affordable ADUs in Portland, Oregon that can be used for this purpose. Homeowners who live in the city can buy a turnkey home for $125,000, or they can rent one for about $1,200 to $1,500 per month.

Take a look below.