Most leases or laws require you provide a heat system that keeps the unit above a certain temperature.

If you are leaving the water on in the property you can purchase freeze alarms that you can place in basements and crawl spaces that will alert you if the temperature drops below a pre determined temp, additionally many of these sensors can detect water so if placed near a hot water heater or water source they can alert you if there is a leak or backup.

The general public (as opposed to people on BP) are about a year behind when in comes to market temperature.

I would think it would not be cost effective to heat your house with heat pumps at that temperature. 

Of course, Spring brings a lot of water and crazy swings in temperature.

The basement is cool, first floor warm and the top second floor uninhabitable on days when the outside temperature is above about 80+.

It's because most of us do not have an accurate "temperature" for the market. 

This is like knowing that normal body temperature is 97.6 degrees, but the thermometer says you’re at 105!

If I was out of state investing I would not buy anywhere with freezing temperatures that last more than a day here or there.

However, I'm concerned about the temperature throughout the house especially as I rent per bedroom and the garage conversion (bought it like this) could be 2 bedrooms or a 1 bedroom flat with smaller room for office, small kitchen and living area.