My main concern is if the pipes will freeze in winter without thermostat controlled heat.

Your hvac contractor should be able to setup a controls package to allow the two systems to interact with one another.Be advised many heat pump thermostats are more expensive then usual thermostats because they’re specially designed for that piece of equipment and you cannot use something like a nest or an ecobee.

In addition to what has already been said, you may want to get a WiFi enabled thermostat to keep an eye on your HVAC, especially when it's empty. 

He then went into the 2nd floor apartment and said the thermostat was working but it was an electronic thermostat and he said these could be problematic with steam heat.

You can use programmable thermostats.

While we usually have our student properties re-rented in February/March for the next academic year, you can still find students over the summer - those who were accepted into a programme late, who's previous arrangements fell trough, or who simply didn't plan in advance.   

As a web programmer, I am acquainted with webhosting issues :grin:

Recently, like this week, Zillow announced a contest with a $1.0 Million Dollar 1st prize to any group of programmers who can help them improve the accuracy of their Zestimates.  

(e.g. nest thermostats, spray foam insulation, or one of Tesla's solar roof systems )  but adding some very basic products that this property was lacking. ( I think a lot of mom & pop C & D properties are in the same There was zero insulation in the attic ( Added R-38)Old Single Strength Wood Windows ( Replaced with low-e replacement windows)HVAC 12 Year Old 10 SEER ( Replaced w/ new 14 SEER HVAC)12- 14 year old appliances ( Adding Energy Efficient Appliances )Definitely the basics, but just making those improvements has definitely directly or indirectly (depends on how you look at it) impacted the NOI and the overall tenant experience.

The boiler system has baseboard radiator heat & 3 new thermostats that must stay since they were all completely replaced.