Although we have not had a pandemic like this since 1918, but we've had similar demand shift in Canada and more recently in the UK.Drop in demand in the Montreal market after the referendum for independence in 1996 has altered how one's investment goes in the long run. 

About 400$ in monthly debt payments can translate into you not being able to get an extra $100,000 or so on your mortgage. 3.)

When I hear "you CANT" my brain translates that to "find out HOW you can via other means", so that's my approach, find out how via other means. 

Rent doesn't matter without knowing how it translates into Cash flow. 

Alterations that include any project that affects the envelope of the building triggers title 24.  

I've been pushing hard for my wife to read Rich Dad Poor Dad, as most would agree this is the best resource to alter your perspective on cash/assets/liabilities, and how they work for/against you.

There would be no alterations to the exterior entrance of the condo. 

Turns out, my rockstar realtor from Memphis said his wife speaks Mandarin and she may be able to help translate.

There is a foundation issue "on the left side" causing a slope/sag that is translating as cracks in the stuco and unlevel floors. 

In response to your question, converting the home back into a duplex can be expensive and time intensive, depending on how much they altered the original layout.