.🌞 In Las Vegas, March signals the start of spring, with daytime temperatures reaching the 60s and nighttime lows in the 50s.

@Alejandro Ferrer you can have thermostats that limit the temperature the heat can be set to but where are you located that you think they can turn the heat off when they aren't home? 

I know pvc is not porous but with temperature in the back side (inside the wall) the front will easily develop this.

It’s the same temperature right now in MN as is it is Vegas.

While using a glue with a floating floor will help with separation issues in variable temperature.

If the heat isn't above the legally required temperature they might declare the unit uninhabitable and boot the tenant out until the situation is rectified (which will of course be a day later when they can come back and verify the temperature is back to normal).

So, I would install a vent that automatically opens and closes with temperature like this:https://www.lowes.com/pd/Air-Vent-17-5-in-x-9-5-in-Plastic-F...3.

These “premium” options will rent for significantly more than a typical bedroom, and having a “premium” option in a house is sometimes the deciding factor in whether the property pencils out.Moderately important: temperature & HVAC control.

The one the plumber sells will cost him less than that, and he may try to talk it up as better than the "big box" ones, but it's probably about the same.Add maybe $50 to that for parts - like a new temperature/pressure relief valve if the new one doesn't come with one, maybe new flexible water lines if it's not plumbed in directly, maybe a new shutoff valve. 

Some of them might have knob and tube electrical and I've owned one where plumbing was fine (all copper) but with the lack of insulation in an area those lines would freeze in extreme cold temperatures.