Be careful. If it is a Coke machine make sure he has a bill of sale for the machine. It may still be owned by Coke. Don't always count on a big return from a pool location. If there is no security, vandalism is higher and because of the moisture in the air electronics might need replacing. Good luck.

I am route supervisor of a 15 route company in Illinois.
We get a month or so of temps in the mid teens or below each year.
If you don't have a lot of soda on the truck it would be safer to remove
it nightly. Set your route up to do soda 3 days a week if possible.
We use just a box heater that will shut off if turns over. Make sure it is not near
anything flammable and pointed at the soda. It also helps putting a
sheet of foam insulation on the walls and an extra board under the soda.
If you can, closing the door while you get your product next to the door
as much as possible. Also, stacking the soda away from the door helps too,
Diet and water will freeze first so protect them more from the cold.
Good Luck.