So my question is, considering the environment and my situation, how should I determine whether a property would be a decent deal? 

A home boasting 4 bedrooms and 1 bathroom, ideally situated in the charming neighborhood of Upper Darby.

Here is the situation.

Send him a DM about your situation.

It's about understanding their situation inside out – not just the numbers game but their personal challenges, goals, and worries.

Maybe talk to a financial advisor or lender who can give you specific advice based on your situation.

I have multiple STR properties on the beach and looking at adding a vehicle to each property to enhance the vacation experience.

You could offer them 1/2 or whatever ratio you feel is fair given the circumstances and they can write you a check for that amount to walk away.Another thought, if there is a way you can find out where they are moving, a forwarding address etc, I'd reach out to that new LL or owner and explain the situation to them, I have a feeling the tenant didn't disclose that they have an existing lease as a liability in their financials when the applied, and there may be some application fraud etc at play here that the new LL would likely want to know.Think about this from your own point of view, I doubt if you picked up and left one of your subway locations that the the LL would just let you leave.  

Not sure how busy he currently is but clients of mine have used him for multiple jobs.

I am in a similar situation, in Russia, where the Embassy is not operational and the consulates are closed.