Quote from @Paul Gupta: Hi, in California, For jobs requiring a license, there was CSLB (contractor state licensing board) which would give either a General Contractor license, or specialty licenses by trade (~60 specialties such as concrete, welding tile, ) https://www.cslb.ca.gov/about_us/library/licensing_classific...My Q: does Maryland and DC area have similar requirements? 

@Collin Hays My favorite that came in at 6am one morning when the nights low temperature was 58 degrees and the high temperature was to be around 75 was the following.

The tenant frequently informs me the interior temperature only reaches 68 degrees.

It might be worth talking to a lawyer but not sure if it's small claims or worth it.Also, you might already have all of these things but for future prevention:- smart thermostat (so you receive alerts when the inside temperature dips below whatever preset you have)- Minut (or similar device) would also alert you to the inside (and outside) temperatures; for example, I have 2 devices inside the house and outside on the hot tub deck.

If the temperature goes below freezing point, pipes might burst. 

I hope you or someone is at least keeping an eye on your properties for break ins, squatters, roof leaks, temperature control, frozen pipes (if in cold climate), if you have a basement and sump pump goes out leading to water damage etc.I just talked to two investors in California that have let their properties sit vacant (no mortgages so paying property taxes and insurance).

It makes sense in places where it has temperature extremes.

The down sides to an all concrete house is temperature retention good or bad. 

We took the highest month of "normal" winter usage we had records on -- people in the house, heat running at a reasonable temperature, washer/dryer running, etc.  

If the temperature goes below freezing point, pipes might burst.