Furnace service?

[Mark Forest]

Well its already cold here in Michigan.  I always cringe when the phone rings hoping it is not a tenant saying their furnace won't start.  I get mail from furnace companies offering one time payments for a certain number of inspections and/or cleanings.  Do any of you use this service? How do any of you in the cold climates handle this?  I would like to have a connection to an HVAC service that will come when I call and possibly clean the furnace when needed.