These guys are only operating in the Bay Area, but this is an idea that could spread, especially if they could buy the granny flats for less than $100,000. They mention the company Node, who is charging $200,000 for a ready-built and installed 600sf ADU if you were to buy direct from them.
https://www.rentthebackyard.com/
If you are looking for a reasonably-priced granny flat, Amazon has dozens of kits for sale if you don’t mind assembling it yourself – the House-in-a-Box:
Link to Amazon Granny Flats
