The Lender is requiring me to have an HO3 policy, however, I am having trouble finding an insurance company to give me an HO3 policy because they speculate that the pipes are prone to freeze and burst in winter due to the home not being controlled by a thermostat.

In a DUPLEX upper level has control of thermostat for air conditioning. 

By Kari Klaus, Founder of RealtySage.comIf you’ve upgraded your home in the past 10 years then you’ve probably added smart technology like NEST thermostats, or why you chose Alexa powered lights and Ring doorbells and likely some energy efficient or water saving features.

You can install a light switch to operate the fan, or you can purchase a 24-volt / 110 volt relay and install a thermostat in the unit.

The AC unit has a smart thermostat that allows them to adjust whatever temperature they would like (the smart thermostat is located in their unit).

Also if you don't already have a programable thermostat, change that. 

Single thermostat/gas bill.

Get a WiFi deadbolt, thermostat, and camera.

On the two-dial kind, the "freezer" one sets how long the compressor runs (it's the thermostat), and the "fresh-food" one sets how much cold air from the freezer is allowed to leak into the fresh-food compartment (it controls a flap in the ducting). 

Often it has a plastic button on top that you can push to close the contacts, even when the thermostat inside the house is not calling for cool.