What metrics do you look at to determine market strength?

Also look at: construction pipeline/planned construction starts, cap rate movements, recent sale activity, population movements, strength of local amenities, employment rates, public school rankings and availability of good private schools, repeat sale prices (singlefamily), rental concessions, and employment opportunities 

Determining whether a market is viable is mostly about looking at rent growth, population trends, employment opportunities, and the strengths of your own organization (to make sure they match the market). If you guys are only good at building luxury, you're more constrained than if you have strengths in building workforce housing. A better question is what makes a project viable. 

If I were going to buy a MF property of 5-20 units I'd probably do the opposite of what everyone else is doing and look for something in a urban center that was crushed by COVID. There is high development/acquisition activity in upcoming metro areas in the sunbelt, but that means cap rates are already compressed. Another option would be to go to those sunbelt areas that are hot right now and buy something on the edge of the urban core/near where future development may come. That future development will add supply (though likely supply that is nicer than what you buy), but will likely by synergistic by improving the area.