The oil tank had 200 gallons in it , I had to help him pump it out , he will use it in his equipment  ( heating oil is diesel fuel ) .I will use the conditioner right away on 1 rental with hard water . the rest of the stuff will be replacements for other rentals I have . 

Single family rental property was bought a few years ago for $42,000.In 2018, furnace and air conditioner were replaced at the same time.

For everything else, they can buy an air conditioner or a space heater and be all alright.

A licensed mechanical contractor should beconsulted for repairs THIS SHOULD RESULT IN A LOT OF WATER ON THAT FLOOR Could not test Air Conditioner as it was too cold outside TRANE UNIT, 2010 A white powdery deposit was observed on two brass valves at the rear of the crawlspace, which is indicative of deterioration of the brass alloy and may result in leaks/failure at the valves.

Another house we were interested in we drove by weekly and saw the cabinets, air conditioner, ceiling tiles, etc. being removed a little each week. 

Material depends on brand, seer (efficancy) location of unit. is there already a air conditioner?

But after we had tenants whose various dogs ate my porch swing, the plug off a window air conditioner (haven't a clue why the dog didn't fry himself on that one), dug holes in carpets down to the subfloor, ate the bottom off a closet door, chewed open a door and got under the house in the summer heat to stay cool and crushed a duct pipe and (in one case) were kept under the house so I got to clean feces and urine out from under there on my hands and knees....we rethought our  idea of the need for a pet fee.Gail

Also they can't test the air conditioner at any temp under something like 45* F.

You must have thick skin in this business, some call me a skin conditioner!

These units are relatively basic, they have individual room baseboard heat systems and wall mount air conditioners (1 each), so not nearly as expensive to replace as a normal HVAC system.