Originally posted by @Justin Thorpe:
Thanks for sharing your experience. I am curious on why you think everyone will like an ADU. I think there will definitely be investment minded folks but most folks would prefer privacy and a distance between themselves and their tenants. I agree with the rest of the points on remote/hybrid work, increasing cost of construction etc.
I think it depends on the neighborhood, the lot size, and the design of the ADU.
If it's a high-end wealthy neighborhood (think Los Altos, Menlo Park, Palo Alto) where all the main houses are giant, maybe the potential buyers would just think of an ADU as a bonus, but not as something they want to pay a lot of $$ for, since they are most likely not going to use the ADU as a rental, but more like a guest house or an office.
However, if it's in a neighborhood where most buyers are younger folks who have young kids and elderly parents (think Santa Clara, San Jose, Fremont, etc.), then ADU is very appropriate as child care and caring for elderly parents are big & real needs among this demographic. Also, a lot of these young professionals want to have separate office space (to maintain work life separation) and can use the quiet space in ADU to WFH. More space is definitely not a bad thing, and nobody is required to rent the ADU out. However, they would have the option to, if they feel like they need some extra cash flow.
Lastly, it's important to know that not all the lots are appropriate for ADUs. If the lot is too small, might be better to just do an addition instead of a detached ADU to create more living space. If the lot is big enough, then a well-designed ADU (with their own private yard and entrance) should NOT interfere with the life of people living in the main house NOR should it decrease the quality of life of the people living in the main house. It should increase the quality of their life by providing more optionality.