I mean I think about it a lot now that we are closing in on 70.. but hey 70 is the new 50 :) And different cultures handle this far differently than others.. this is why you see some new builds catering to multi generational floor plans..

They were unable to do so and have ostensibly walked away from the project leaving their partners to clean up the mess.

Like the push to get tiny houses accepted and zoning changed,   a "cleanly well run rooming house" business model has yet to get much muninicipal acceptance tracktion.  

I have a DADU over my detached garage that my daughter used to live in, but now she is out on her own so if I want to do a more major renovation (need to refinish the floors and maybe open up the kitchen more), I can move into the DADU as well.

OP said: It’s frustrating, especially because our due diligence came back clean, leases were solid, and the property had just been fully renovated.

That would be a foundation issue to make sure the current foundation is able to hold two more floors on top and also a height issue for the town for the area.

Open floor.  

Fix Flip- only do surface style changes- flooring, landscape, roof, windows, etc. 

But it's a 3/2 and I think I could rent it for $1000-1200, has a lot of NEW things already in it (AC/heating, kitchen cabinets, appliances, flooring) but bedrooms need to be finished remodeling. 

Do the Airbnb discounting, price a little under market, make sure your cleaning fees are at or below average, looser cancellation policies will all help.