Isn't it unlikely that a homeowner who cant afford a 2-3k tax bill would even challenge this legally?

Tokenization of real estate assets can take numerous forms, but what you’re proposing is to separate the real estate “bundle of rights”, have the property owner sell one or more “rights” but not all of those rights, and represent the ownership of the rights that have been sold by tokenization utilizing block chain technology rather than the county “filing” systems currently in use.  

Quote from @Bill B.: It’s kind of like asking what’s the worst part about not being a real estate investor?

The investor “gave up” after numerous attempts to sell the lot or get a “refund” from the county proved unsuccessful.  

You have numerous funding options so pick your poison.

I can find numerous other similar homes for investors.

Search the BP for ADU appraisals to encounter numerous examples.

Hi, Jorge - My MTRs are in California, too, and we have exceptionally high bills in the summer time especially for AC usage.

Consider energy-efficient upgrades like LED lighting and smart thermostats to lower utility bills.

You do not actually need any income if they have high enough income to afford their bills plus your new house.