My team has gone through this very experience one to many times this past winter.

a) they might vacate in middle of the winter, when it is least convenient for me. 

Challenge is that the garage is not insulated at all so it's pretty hot in summer, pretty cold in winter.

@Erin Anderegg as @Greg Scott stated, not a big problem in Michigan due to winter frost killing most.

We got to partake in the neighborhood winter decorations.

Single slope to take snow melt to the Sunny side of the pavement during the winter.6. 

I would say keep looking for leads and in maybe look in the winter when their jobs tend to slow down a bit more?

We were still able to cook normally with our propane stovetopWood-Fired Stove: not sure if your cabin includes a wood stove/pellet stove or if this is a feasible option for heatFilling the bathtubs with water before a winter storm: and voila you can flush toilets, include a big stock pot for warming up waterIf there's a spare small closet or cabinet you can lock (and have guests access via a lockbox) with winter storm supplies for your guests such as gallons of water, camp food packs, emergency solar/windup charger for phones, matches, etc to help them weather the first few days and save your booking that may be helpful as well.

My grass needs weekly mow in spring and fall, bi weekly in heat of summer, and snow removal during winter.  

Sales are also slower in the winter in northern areas at least.