Here’s how it works:Population Decline or Stagnation: If the population is static or shrinking, the current housing supply meets demand, and property prices decline (in inflation-adjusted dollars).

While I use it primarily for noise concerns (it alerts me for sustained +80 decibels), it's also handy for cigarette smoke and tracking temperatures (in addition to our Ecobee thermostat)- sensors on all exterior doors and possibly windows (which you might have via smart locks for the doors)- exterior camsA recent guest for reasons only known to them set the thermostat to cool and 60F in the winter (where it's currently a balmy 11F). 

Due to inflation and the drastic increases in material, labor, and supplies, that's naturally caused carriers to rethink limits/values on file. 

Actually buying these apartments and not the current supply is a good opportunity.

Customer supplies materials ?  

Other low-cost amenities that can boost ROI include a coffee and tea station with basic supplies, a welcome basket with snacks and water, or small outdoor games like cornhole.

I'm reaching out to other plumbers to be safe, but are those supplies mine to use now for the next plumber?

It is about supply and demand. 

Selling to the wrong buyer can become more expensive than carrying the home for slightly longer.I will buy my bath/kitchen fixtures at a plumbing supply house and not a big box store.

You mention Amazon, look at how they play suppliers off each other and even create their own supply chain.