More cost effective, if someone time consuming, would be to change the most vulnerable pipe to high pressure PEX; I've seen demonstrations of PEX expanded absurdly beyond its size, with pressure and temperature, before busting.

Talk to some mortgage guys and get the temperature on that right now.

Floating snap lock floor is floating so it moves and temperature differences will make the noise more noticeable.  

I can save money on electricity when no one is there and monitor temperatures to make sure I don't see one of my HVAC units struggling so that I can arrange for service before there is a failure.

I am in Oklahoma where temperatures are often 100 + in the summer.

Also, remember to bleed water lines (for all garden hoses) so they don't freeze up on the first day of freezing temperature! 

.- Set thermostat back to certain set temperature- Lock house and return the key to the lockbox (if needed)Any more than that and I think you quickly run into the "Well why am I paying for housekeeping services then?"

- If you are sharing Heat/Air with your tenant, how do you handle temperature adjustments?  

Would you rather be home based in the Bay Area with tons of things to do nearby, good weather, lots of nature, etc. or someplace with little culture, extreme temperatures, bland immediate environment, etc., etc.

Those systems need flexibility as they expand and contract with temperature changes, and you will have problems with the field seams if there is something that restricts movement - like base cabinets on top of them.