I have a 3 unit building and the basement is dark, little ventilation and gets really humid.

Clarksville has 4 seasons and the humidity is not as heavy as it is in Florida.

@Jim Cummings One way of setting up automation for HVAC is to have nest thermostat, get periodic data from it, do some processing based on outside temp and humidity.

These are wifi so you can monitor temp setting, actual temp and humidity.

Put up a little sign by the thermostat that explains that running the air conditioner at a low temperature in a humid environment will cause any central air unit to freeze. 

However, humidity is high in Ohio summer and the walls get condensation without dehumidifier on constantly.

High Ohio summer humidity causes condesation on walls if dehumidifier isn't on 24/7.

Had to replace a garage door opener and a microwave so far, about $300ea  We’ll either move there or raise the rent in 2021 as we decide if we can tolerate the humidity to live on the water. 

Since this place is in NJ, humidity is a factor, much like Maryland so you'll want to look for any discoloration (i.e. mold), especially in the bathrooms, under the sink, basement and attic.

So, I've been in this landlord game quite some time now, and my second largest business expense is mildew abatement.Let me explain.Most of my properties are in Monterey County, where we get a lot of humidity.