Depends on size, brand, type (electric, gas, electric heat pump style).I just replaced my gas one at rental and I went with the 12yr rated one and bought the Allstate protection plan for $69 that gives me 5 more years after the 12 yr manufactures warranty. 

I've seen them written where the Tenant handles all maintenance except for the structure, which means they cover heating, plumbing, electrical, flooring, ceiling, doors, and windows.

Many have boiler heat and A/C wall units.

As long as it's "heated sq footage" it's as easy as calling the property appraiser and getting the sq footage added to public records.

Hello All,This summer we have seen several maintenance requests for AC breakdown and with the heat this year it has become very difficult to keep tenants happy while AC unit it repaired which might take 2-3 days depending on parts needed.

Conventional / FHA loans have a minimum standard for the condition of the property they will lend on (ie must be livable, have working stove and heat).  

Not something landlords are happy to hear, but… the typical market trends tell us the markets usually cool off towards the end of the year and then start heating back up mid first quarter.

The crawl space was not really properly constructed in that was build with some basement concepts and come crawl space concepts. e.g. the insulation was in the joists with facing down - yet the mechanicals below that and with the opening to the basement, it is a "semi heated space" - which is good because the water lines are not insulated.

See if the installers put heat transfer tape between the metal roof and the metal beams so heat doesn't transfer inside the building. 

Usually costs more for electric heat.