I sent them a text with an informal notice that if I don't hear back from them about the changes in their arrival plans and don't receive the first months rent by tomorrow I will presume they no longer plan on taking possession of the property at which point I will make a formal legal notice.

I'm starting to notice that more investors (specifically Class C areas where one of my Indianapolis rentals is located) will advertise that "appliances and AC unit to be installed upon move in" for their rental or flip for the tenant or buyer.

And whoever makes the payments on the mortgage could stop, resulting in a notice of default, leading to foreclosure…making this a risky situation for the wife to be in.  

Have her served TODAY with a three day notice.

I've noticed homes 30% larger than mine are paying about 1/3 of my tax amount.I know I missed the appeal window. 

Also, if zoning restrictions were to be relaxed, could the area end up like others with abundant supply, potentially leading to a decrease in property values?

Just lean heavily on educating yourself on the laws, notices, etc. early on.

But historically in my experience it was never done on time and i would get notices from the city about it.

Jack MillerI have not had any tenants not pay rent, but I have seen rents soften for multi family and condo rentals (roughly 5-10% decrease in rental rates). 

One of the 800 economists who work there may have told them that since they decreased the M2 money supply by 4% over the last 2 years and currently now growing at only 1.26% not the pre-covid 6%, that they have stalled the plane, so forget the soft landing, get ready for some CHOP.