Vacant houses are subject to getting the Air Conditioner Condenser ripped off.  

The installation costs should be lowest for baseboard electric- and even though it's the most expensive way to heat, if it's only used one day per year, the impact on the electric bill is the last thing you should be thinking about, as it will be negligible.I also like @Marelyn Valdes' idea- she's suggesting a heat pump, which essentially reverses the direction of the air conditioner(it "air conditions" the outside, thus transferring heat from the outdoors to the interior.)

As for the hole, there is no "weep hole" in window air conditioners anymore either.

There was some mold in the closet being caused by condensation from the air conditioner.

I'd look into the possibility of installing heat pumps with electric heating elements for very cold days(one per unit, hopefully, in the units which currently have electric heat) these can be installed in the window much like typical air conditioners and they will function as air conditioners in the summer- some can be installed through the wall.

One item is a window air conditioner mounted over the electrical service.

Sanded, wiped, used a wood conditioner and then stained and polyurethaned.

If the damage was on the receptacle, I'd get a new receptacle, but if it looked like the wiring was damaged, I would think real hard about rewiring that circuit with copper.If you have an electric furnace or electric air conditioner with aluminum wiring to them, those may take a little more work. 

If it were me in the situation I would look either at the most doors I could get for the buck in a stable market, like a $750,000 16-unit multi-family in my market that is currently c-class (window unit air conditioners, dated stylings, and 10+ year old appliances, etc), extremely well located, and, based on all that, probably a good target for adding value over time and increasing the appraisal value substantially. 

We are working to add air conditioner or heat pump to 15 new 14'x56' homes in SC.