I'm currently in construction on the lower level of my house in Oakland, which will be split in half and include an ADU (accessory dwelling unit) that we'll be able to rent out.

There are two ways of doing this in Oakland, and presumably most places - the Legal proper way, and the not-legal way. Most seem to be the latter.

But we wanted to do things right. Oakland has a housing shortage and we have more square feet than we need, and we were renovating the house anyway. And according to the city, they're trying to encourage ADU's to help with that housing shortage, so we went that way.

But that means we're subject to a whole new set of zoning and construction regulations. Originally I wanted to keep a (locking) interior door between the main house and the ADU so we had the flexibility of having it as a guest room or literal mother-in-law suite if we weren't renting it. Zoning shot that down - ADU is required to be completely separate space.

Oh and that 'separate space' is quite literal. Separate HVAC, separate electrical, separate sewer plumbing to the lateral with separate cleanout, and 1-hour fire rated separation on shared walls and ceilings.

Some of that makes sense and I'd want to do anyway, but it means a simple 400sq. ft. 1 bedroom ADU in an existing building is about a $100k buildout.

The previous owner rented the downstairs space as it was - not legal, no real separation from the main house, shared everything. That was pretty much free for her.

I wonder if there's a middle ground somewhere. A 'legal' way to dense up our housing but without the great expense of rebuilding it from the inside out first. This seems like something that we'll be seeing a lot more of in the future, but I can't imagine most people will want to spend what I'm spending to do it 'legally'.