These can work well for family members with intellectual and developmental disabilities…

https://www.marketwatch.com/story/more-people-are-turning-to-this-housing-idea-for-aging-parents-but-obstacles-still-exist-in-much-of-the-country-11652388107?mod=bonds

Check out California information: Accessory dwelling units.

https://www.hcd.ca.gov/policy-research/accessorydwellingunits.shtml