I will definitely screen my buyers more in depth in the future to prevent this from reoccuring. regarding the continued marketing clause, I came up with this to include in my contract. 

The condition, age, and future capex issues are more important in my opinion.

I haven't worked with them, but I'll save their info in case I have future stuff to do. 

I'm considering upping my aggressiveness on remediating this issue with something that will cover up the color of the mold so it will indicate better remediation efforts to future potential buyers. 

Ready to sell and invest in house, condo, or multi-family with good ROI and future growth.What made you interested in investing in this type of deal?

Desirables: 8 min walk to trains to NYC and 2 parking spaces.I feel the property was not built well and future leaks are inevitable. 

Much cleaner slate for presenting future developments to the city for approval. 

Rent Relief (I think it came from the Covid Rescue Plan) just paid 7 months worth of rent (past and future rent) as well as her water and gas bills.

Here is a relevant link, again hard to find the dirt so hopefully biggerpockets will rank this in relevant search to save others in the future!  

In the near future I may look at another conventional or a dscr.