The Lease needs to be clear in its definition of what you are trying to accomplish here which is that the Tenant pays for all of the operating and maintenance expenses of the property.In addition be sure to include an understanding of who pays for major capital replacements (not just maintenance) such as replacement of the heating and air-conditioning units, water and sewer lines, electrical mains, roofs, glass, etc.

I think central heat/air could go out of style if ductless heat pumps become cheaper and easier to install or if window/portable heat pumps become cheaper, more compact/sleek, or more efficient.

Turn the heat up on the tank for $60? 

This thread got a little heated.

Most do not have central heat and air systems.

@Mark Ainley is right, Logan has heated up in recent years.

heating gas $3500 / electric $272 / association $4500 / permit $500 !!

The moisture in the air is condensed into a water vapor and heated up, then it passes through the liquid nicotine.

The heat pump works fine but is at least 20 if not 25 years old, the house also has some big trees too close to the house where big branch's have already fallen off the tree and have done damage to the roof in the past (I can tell by the patched shingles). 

Out of 4 rentals, I have had 3 A/C units go down due to the 100+ heat index days we have been having this summer.