I welded the middle 3 point hitch with 3 car batteries, some jumper cables, vice grip pliers and 1/8" 6014 welding rods.

While the air temperature is above zero during the day, the basement is very frozen and not likely to thaw any time soon.

That way you set the temperature, just like some apartment buildings, but then again the tenants usually can control it somewhat since they usually have a valve to control the water going to their heater.

If he says anything make a note of it and even document the temperature outside that day because he sounds like an unethical jerk.

I'm doing a temperature check here to see how much interest is out there....Paul

The newer valves are pressure-regulated, so if a toilet is flushed (or another shower is turned on), the pressure may drop a bit, but the temperature shouldn't change much.Maybe it's easier/cheaper to upgrade the shower valves than changing the water heater setup?

You can loop them into separate thermostats so you can be pretty specific about individual rooms and temperature without adding a ton of cost so long as you don't go overboard.

I think doing anything roofing,  electrical, plumbing, welding, or any specialized trade will take much more work/certification to where you will probably want to make it a career.  

This means that the guests in the downstairs apartment will not be able to adjust the temperature.

They don't move in 30 days, you place the order with sheriff, but its now winter so its too cold and a blanket-stay is in place until temperatures warm up, 1-2 months delay.