anything that restricts or impedes what you can do with a home is a liability, not an asset. Up in SF, even partially tenant-occupied homes typically sell for a sizable discount.
(also doubt that ~10k/year is going to make waves in the target market -- Bay Area homeowners with a back yard big enough to make this viable.)
It's worth noting that this is actually something the article wasn't great on. If your buyer is excited about continuing this agreement, we're happy to sign the unit over and even take a second position to a new mortgage so you don't ever need to pay anything.
The great thing about a backyard apartment is that it is a permanent improvement to your property and increases the value of the home but you have a great point. We aren't the best short term partner. If you don't plan on staying in your home for a long time, making substantial improvements to your property doesn't make sense. We're focused on helping homeowners be able to stay in their home as the cost of living rises. We're committed to doing the right thing and turning away prospective customers who don't fit this profile.