Battery charger, turn fridge on before trips, Dump station, Concierge parking service, Tire/Oil/etc check, Big drive ways, electric in each unit, etc.Canopy, I have seen in Texas.

Further west, the cost of natural gas is sufficiently less than electricity and oil that it may be more "cost effective" to burn natural gas in the shoulder seasons even if it is less energy efficient.

A few numbers missing from your calculations that you should consider adding in:-Heat (is it oil, propane, electric?)

Therefore, they may be willing to pay $20,000 more for a home than i would, not knowing that the property needs a waterproofing system and mold treatment, or has an underground oil tank, or has termite damage, or ignores the 25 year old roof, water heater, and furnace. 

I think a lot of investors will make lemonade out of these lemons. 

While it goes without saying that finding deals is the most important aspect of the business my question would be what is the number one tool or system to have in place to sustain a well-oiled machine and business that could potentially be sold at a later point in time.

And verify the property tax bill by checking the tax assessor's website; because the MLS always has a disclaimer as to accuracy of nay numbers being given.My guess as to why it is still on the market: owner paid heat, due to only one central heating system - and if you find that the heating fuel is oil, you have another knock against this property.

I have been aggressive in getting rid of oil heated building by either selling or converting.

If the local job market depends upon oil and gas for example and oil and gas drops and many jobs are lost that will really hit you. 

Also a future business partner who works in the oil field and has more money than time.