"[A]t no cost to the public"
I like the idea of ADU's as a part of increasing our housing supply. Joe and I moved here from Eagle. When we lived in Eagle, we bought the cheapest house in the county and built an ADU in the back. We rented out the original structure and lived in the ADU. It made our property very difficult to sell. What was once the cheapest house in the county was suddenly more expensive and banks had a hard time wrapping their head around the concept of a home with an ADU. The same thing is true today. If one were to buy a $300k home and build a $100k ADU, now they have a much more expensive property to sell. Even if the ADU has a positive cash flow, the buyer would usually have to qualify for the mortgage without counting the income from the ADU. While ADU's can provide more housing in town, they really can hamstring buyers and sellers in the future.
Nice. How about lock-offs, also?