It's more costly than a thermostat, but a permanent solution could be to remove the ducts from the 2nd unit giving the 1st unit the entire use of the AC system.

Speeds are pretty good, easy to use, and overall a good solution for locations that have cell service but don’t have wired internet options.

@Tristan WhiteIm not very good with direct mail, but if you send postcard which is only 35¢/card it'll  be 36% cheaper.Im sure there are better solutions out there. 

A business that at least tries to improve/come to a solution with a customer (whether a legit complaint or something that's picky or straight up not true) is a positive. 

@Dilip Ra Nordic Home Solutions in Smohomish, WA do fantastic work.

Obviously, the tenant is most likely not looking to spend money on a water bill that includes the irrigation of watering the lawn, so I am trying to come up with a solution possibly to continue utilizing the irrigation with City water but still have the tenant responsible for the water bill.

The bank account will serve as your basic book keeping until you need a more sophisticated solution like QB. 

To Matt's point everyone looks at the pictures - maybe that's your solution... ?

One of my solutions is to house hack by renting out rooms in a single family home, vigorously save, and move out in about a year to make the home a full-time rental and repeat the process.

BP community can give you some good ideas where to start and provide some solutions.