Found the perfect multi-family! But...mold.

Have found a four unit multi-family and the seller is in pre-foreclosure.  It’s in need of serious rehab (new kitchens, new bathrooms, new floors) but am more concerned about mold/moisture.  There's definitely mold on one of the walls in one unit and potentially mold around the windows (the termite inspection int the disclosures mentioned fungus in a lot of places).  And in that same unit, lots of discoloration on the floor of one of the toilets, looks like water damage.

This would be my first multi-family -- did I pick a bad one?  I'm worried that the mold damage is so extensive that the house will need gutting.  And the mere mention of it has scared off a few lenders, who have said if the appraisal comes back subject to repairs, the mold will have to be remediated before closing.