When pockets of generational poverty exist within certain areas, its really hard to have assurances that there's not lots of risk to equity over time. 

However, the further outside of Boston you look there are more favorable numbers.I bought mine a little over 2 years ago in Quincy and live very cheap in a nice two family home while occupying the larger of the two units.

I'm evaluating a RealtyShares.com common equity investment offering for Twin River Commons in Binghampton, NY with target return 14%. 

After I find “tenant/buyer” for “seller/me” for the “home owner”, I want to leave the deal because of no equity, or I just don’t want to stay in the deal.

Will it actually add equity?

If you will wait you  can cash out higher equity.  

There may be variable stipulations about what percentage of the equity each Lender is willing to "Cash Out". 2.

Does anyone have ideas of how best to tap into the equity of a non-owner occupied building so that I can fund another deal?

There is enough equity for me to take out a loan now.

Like I said if you get a deal for 25 cents on the dollar, with not much rehab on a deal worth 100k at very least you dnt pay they get a deal with great equity.