First time home buyer looking to house hack multi family in NH, but values at 600k+

[Mike Silva]

Hello!
I am looking for some advice on house hacking in the state of NH. I have been looking since December and have noticed the multifamily (specifically duplexes) prices increasing past the 600k mark. I am seeing half the properties cash flow and half don't. After listening to more Bigger Pockets podcasts, I as starting to learn there is more to this than the cash flows. 
So my question is to all the experienced investors out there: 

What metrics other than a Positive Cash Flow and Net Worth Return should I be looking for when purchasing a multifamily to house hack?