When I was a masters student at UMD in 2006-2008, I was involved in advocating for this alignment w/ @dwdaddio, versus a circuitous route preferred by the president & faculty senate at the time. If you see bad decisions, speak up, you just may win!
It was good for us, but only because the second hand price was a fraction of what it would’ve cost to build. It took a lot of work and research and we’re still learning.
In short, ADUs are a pretty bad investment if you are building it. If you want space for personal use, build it in your main house. If you are going to rent it, be in it for the long haul. If you buy one second hand, it could good or a total pain for the faint of heart.