This makes running any cash-based financial metrics a lost cause...my returns are infinite-ish.

In your situation, I would set the firm move out date but holding them accountable for paying the rent might cause friction. 

Now that it's empty, I'm faced with a dilemma because of my fears that the market will crash later this year/early next year as a result of a virus resurgence causing high unemployment and associated economic woes, plus the cyclical downturn that was predicted even pre-covid.

Im hearing that attorneys haven’t got the deed from title company yet and Covid is causing delay in getting it back from the cook county.

I occasionally would hear opinions that 2008-09 was a once-in-a-lifetime event and the next recession will be more mild, plus it will probably be caused by something other than housing, implying that multi-family won't fare as badly as it did back then, which wasn't bad at all for some operators in some markets.

I am going to comment in here mostly to track replies from people with more experience....however, I think it's important to remember that there is a wide range of situations that can lead to the missed payments causing a home to show up as "pre-foreclosure" and different approaches would be appropriate for each. 

In contrast the 2020 recession is an outcome of a pandemic which is causing economic havoc but homeowners and lenders all seem to be in much better standing now.So what drives this thinking that home prices are going to crash the same way they did in 2008?

She hides the dog in the house, a therapist calls me, I speak to her and inform her I need documentation for the dog, I also inform her that the dog looks neglected, is unsupervised, causing damage to the property and creating conflict with the existing tenants in the triplex, she ignores me and a letter on community health department letterhead shows up claiming the mutt is an emotional support animal.   

If your friend is noticing a problem with the sewer and didn't get an inspection it probably can't wait because it is already causing problems, it might be slightly cheaper if you do it in addition to extending the line to an ADU. 

That is not to say I have stopped looking for good deals on already built properties, but it is no longer my only strategy and is no longer causing me angst!