It takes a pretty specific type of property to accommodate an ADU and it has to be in a specific location to make the ADU worthwhile. If you're in the suburbs you also have HOA rules to contend with. The only place we could put an ADU in our suburban house is to build out our 4-car garage -- it's large enough (and we onyl need 1 car), but we'd have to build a bathroom and a kitchenette. But even if we could afford the initial substantial outlay, I don't think we'd have a lot of takers as people who are likely to rent an ADU typically need to live closer to the city.