We'd need to know more about the property: location, configuration, age of building & major mechanicals, etc.

For example, the strategy I will be doing is medium-term rentals with an emphasis on traveling RNs.Original post I was referring to: Rent out the whole house or Rent by the room?

Like @Julie Rossman mentioned, you could try calling up SHAG HQ and asking them about that kind of investment, there is also Aegis Living, Merrill Gardens...all would probably be good opening moves to take a look at the mechanics of this type of investment.I do know a few property managers/facility engineers at the aforementioned companies that I have interacted with professionally and could point you in their direction.

So my long winded question is, in making purchase decisions as a buy and hold investor should primary emphasis be placed on return metrics (ROI, cap rates, CoC, etc), with $/SF a secondary measure, or should it be a prerequisite that the $/SF price be at or below market in order to protect yourself in the case that you need to sell?

That would be like taking your car to the mechanic and having them tell you they're going to need you to provide a socket wrench....as for materials, we DO sometimes buy the materials, but always discuss it first with the contractor so it's clear who is providing what.

The mechanics can vary depending on the situation and your and your accountant's preferences.

Depends you want to learn the mechanics of apt operations? 

Also, cash flow is a defensive mechanism when things go wrong (i.e., vacancy or HVAC replacement).

For context, I currently work as a Mechanical Engineer at a Consulting Engineering firm here in Austin. 

I am a new agent in Nevada who just passed the State and National tests and can tell you that there is NOT an emphasis on investors in the information.