Add a couple blocks to the joists, some joist hangers, and you'll be fine structurally.The mold is much more concerning, one for the cleanup where you can see, but also there's moisture that's causing it. 

All that white and black fuzz is mold from moisture.

Good that they are trying to remove the moisture.

It is not in a flood zone, as it is up on a hill, although there was some moisture in the basement.

However, I've read to proceed with caution when adding insulation to old brick building (100+ years in my case) because it can result in freeze/thaw damage due to increased moisture, rotting joists and beams that are embedded into the wall, etc.I believe one of my upstairs units along the same wall is lacking insulation as well, which has resulted in frost in the drywall on really cold days (see attached pics). 

My lines are old cast iron and when it gets really dry, those trees are 'smart' enough to seek out any moisture. 

As Jimmy said, it is a combination of moisture and cold temps.

.- All the patio doors were aluminum and some had broken panes that were letting in moisture- There were consistent tenant complaints about the utilities.

The bathroom corners were wet and had some moisture, They said water over-leak could be the only problem.

Recommend clearing theproperty of all excess debris prior to close.Exterior 5 The back porch has settled, the support posts are crooked and failing,the floor has moisture damage and rot, the stairs are leaning and areopen and narrow.