., if the air is not working in the middle of summer we keep extra window shakers on hand to haul over and place in bedroom windows). 

After 20 years in the Air Force, I'm now under contract on my first multiplex. 

I thought it might make a very cool Air BnB but aside from that it was huge stretch to make the numbers work with any other use.

No central air (wall units) old buildings.  

So did this 70% rule just get made up out of thin air?  

If so when you leave the galvanized pipes empty and open to the air they will start rusting.  

In over 22 years of landlording, we have never met a smoker who didn't eventually smoke indoors once the weather turned bad, in spite of our no-smoking policy.We impose a $50 fee every time we catch someone smoking on our property (inside or outside) or have sufficient evidence to ferret out a confession.

You can always pressurize the domestic water lines with air and check that way . 

Leave the shed , it adds value , it has electric and what appears to be a air conditioner .

It's mostly a bunch of hot air to try and buy themselves time.