I have had roofs cleaned by companies who do the low pressure washing w/ chemicals.

I got another quote for spraying (I forget the chemical) for ~350, and it is a local company my house cleaning company recommended.

Chemicals and h2s gases will eat the metal studs alive in a very short time. 

To me, it means they are responsible for ordinary maintenance one would do as a home owner, which means changing out the filter or adding chemicals to the water.

They are not as cheap anymore as you would think, and they need a LOT of work - cutting for the windows/doors is a pain, the interior wood door has been sprayed with deadly chemicals, etc.

Cleaning the coils chemically and regularly, helps extend the life of the unit (particularly if located on the outdoors on the ground, in an area dogs roam) and depending on the age and type of unit there may be other internal points of maintenance to perform as well.

YOUR in MICHIGAN,,, not Florida, or CaliforniaRenters can't and don't like to pay to heat them put chemicals in or clean them.Insurance isn't that expensive but the headache and potential for injury or loss of life would make me FILL IT IN.I've managed complexes with pools,, and our company had one death at another complex,, All I can say is fill it in

Buying a building with a huge old gas tank, lead, asbestos, chemicals, lead paint can cost a lot more than $200,000.  

Any changing of chemicals, depending on the state, could result in environmental filings/records being required. 

Even if there was never a chemical spill, future buyers might be overly concerned about this question themselves.