But, tenants are humans and human nature is such that inherited tenants are usually a pain in the rear. 

Getting rid of a paying tenants who are a pain in the rear is not worth it.

Boilers are a pain in the rear. 

That's just to cover your rear in case anyone files a complaint against you for discrimination, which I can tell you is so rare it never happened to me over many years and hundreds of applicants. 

A pain in the rear. 

Most septics have their drain field in the rear of house and most city connections are in the front of house in roadway.

Then I moved the old 4x7 main bathroom to the rear of the home expanding it 7x15, with room for a stackable W/D.

The abatement was for substandard conditions on the rear unit.

your instincts are correct that even if its a "flat rate" fee every month, or a "billed in the rears" system either one works well if you don't want to actually get the system sub metered.  

You need to ask the city to give you a print out of your setbacks on your property, usually 15ft from the property line side to side, and 25ft front or rear.