The temperature in the Portland area in my opinion is that many people are trying to adjust but validate.

As a buy and hold real estate investor, can you charge a tenant for repairs if they do not take precautions during a freeze by opening cabinet doors, letting water drip, covering outdoor spigots etc. which cause pipes to burst?

If you have water stains there, chances are, the house will need an indoor or outdoor french drain as you have water seeping through the walls and/or where the wall and slab meet.

There are indoor units that have plumbing to route exhaust outside and outdoor units that are simply vented.

The hot water temperature was 140 degrees F at the time of testing.

Fall & Spring HVAC Service Target Date: April and October This service can aid in early detection of costly problems and save the cost of expensive, emergency service.A/C Service Includes: Check condenser coil, adjust operating pressures, monitor safety controls and starter capabilities, clean or replace filter, adjust blower components, calibrate thermostat, measure for proper temperature differences, clean condensate drain, tighten electrical connections, measure voltage and amperage on motors, lubricate moving parts.

With air tests the company should have a calibrated machine, take samples in several areas of the home (conditioned areas) with the control sample taken outdoors. 

Another solution may be to vent the attic space, if it is getting to hot up there and cool downstairs, that will cause humidity at the ceiling and  while your at it check the insulation in the attic, make sure there is enough to keep the temperature difference between the cooled space and the hot attic. hope one of these helps you.

I'm looking to purchase my first property and am currently looking at a turnkey house with a large deck outdoors (12x24x5 ft).

You can add temperature and moisture sensors too.