Just to be on the safe side I would pump pink RV anti-freeze (good to -50) through the rads & lines asap because the winterizing attempts, I've experienced in the past, will NOT be effective at these temps. 

Tempe is a great area, but the MFR's there are pricey.

No one likes to move in the cold temps for sure!  

@Mike Kehoe I would say hold the cash and wait until the market turns, my dads says it best opportunity usually comes when there is blood in the water, if anything I would consider financing a duplex with a portion of that money down, but I wouldn’t get into any fix and flips right now, especially knowing that you could potentially buy those same properties for cents on the dollar in the near future, I know of a few duplexes in the heart of Tempe that are currently for sale but in my opinion they are a bit overpriced based on the Roi but let’s talk if your interested,

Yes, the tenant can adjust the temp from the TRV, but only downward if you have the main thermostat set properly. 

The heavier copper will help a bit according to a plumber, but having numerous days long of freezing temps might still cause problems with no other measures.  

As Jimmy said, it is a combination of moisture and cold temps.

@Gary CarverI love Tempe AZ!

A temp tax increase, but it is only for one year.

Phoenix, Glendale, Scottsdale, Tempe, etc..?