Hate to be the bearer of bad news but temp right now is 14 degrees, getting into single digits by morning.

Using a thermometer (IR, digital, or dial), measure the temperature of the air at the return or as close to the blower unit as possible.

Or is it one of the renters who locked themselves out and just decided that was they easy way to get in.Because if it was a renter (or from their household), a digital keypad code with a different set of digits for every renter might do the trick for a lot less money.Good Luck!

There are keyed/digital locks out there.What does the lease state? 

My skills and include education, community partnerships, design, tech (including 3D modeling and digital fabrication, audio production (could help anyone interested in starting a podcast :-) My wife who is my partner is an amazing artist and interior designer with degrees from Moore College of Art and Design. 

Both are experiencing double digit appreciation with very low taxes as you know.

Peoples needs and motivations vary a great deal, and, while very broad generalities may be valid, it is not reasonable to assume that the criteria for buying a home, renting a home, buying a car, and obtaining a credit card can all be optimally based on the same three digit number.

Or are these sellers just really under prepared for digital communication?

You may not understand the laws or contracts and get yourself into a pickle.I sold my first home as a FSBO in 2000 using the newspaper and an attorney.

Many if not most of the time, we modify the payment to keep the borrower in the home and we are seeing a double digit return from this.