That may have been what the auditor was referring to ("thermostat was wrong") The condenser outside may also not be functioning properly which runs the electric heat more often.

Tax records, go to your county's auditors office. 

What are the other things the auditors commonly look at?

In my other life, I work as a medical coding auditor.  

An auditor may try to argue that you did not have the intent to hold for rental purposes. 

I looked on the auditors site and saw that the owner doesn't live in the state.

I am not one, but I am a full time tax auditor for the Treasury department.

I currently work as a HVAC designer/energy auditor for commercial, multi-residential, industrial, and institutional buildings in Canada.

My suggestions are:2 years of bank statements for the property so you can verify deposits and expenses tied to cash2 years of tax returns (2013, 2014)2014 and 2015 Profit and Loss reportsRent roll for 2014 and 2015Ideally all of the last two are certified financial statements (meaning they've been reviewed and signed off on by an independent auditor), but chances are they won't be.

I did not call the auditor/treasurer to verify this.