During COVID moratorium periods it was not so unheard of to accept partial payments - this is what tenants were supposed to be doing if at all possible to avoid nonpayment all together.  

Also the first floor has the back bedroom already cut into the hall closet and the back stair for a supersized bedroom (the whole square footage of this apartment is now almost 1600 sq ft, which is unheard of in triple-deckers) and I didn't want to undo it.

Not unheard of but not common either. 

That's almost unheard of these days, and your situation just happens to be at the mercy of that. 

It is not unheard of for my clients to be making $1000 on top of their mortgage while they occupy the home, and are living for free.

I'm super impressed you found a house for $750k- Unheard of! 

Also, it isn’t unheard of for the park to give discounts to certain renters for doing things at the property… Like mowing the yard, or even collecting the rent from the tenants.

Ive seen lower income area multifamily in bad neighborhoods sit on market 60+ days which is unheard of in South Florida, I've driven by these homes and seen tenants leave piles of trash out in the yards, broked down junk cars,  and a few drug transactions so I can only assume they are not good tenants. 

unheard of yup..  

Can I refinance into a conventional 90% LTV or is this unheard of?