Some of it looks to have a horizontal pattern with fairly regular spacing, and I would guess that those widths match up with the slats that go under the old plaster and lath walls (what they used before sheetrock).I’m also going to guess that wall has no or little insulation in it (as the entrance to a duplex, it wouldn’t be living space that needs to be heated)So I would guess it’s being caused by moisture that’s condensing on the interior surface of the wall. 

I just got a monthly plan for 2 exterior cameras and one interior camera with motion sensors for our project that is 1200 sq.ft costing $65 bucks a month.

She offered to take classes or study up on a topic so that we can save money or make more - but I couldn't think of anything in particular (interior design was the best I could think of).

With regard to the interior condition, it's reasonably nice for a college rental.Would welcome any other feedback you may have.

The basement was fairly dry before, not finished but had drywall on edges, studs on the interior, poured cement floor, and luckily a French drain around the perimeter.

We get lots of activity due to the great location, reasonable price and updated interior but the loft ceilings and other quirky factors make it less appealing. 

See what Ideas your Realtor has to create a bigger presence for the property-New photos: The photos here are a bit bland and you may want to reach out to local companies for better exterior photos, and virtual staging of the interior/digital walkthroughs to show that even at the list price the house is a value -Open houses: The open houses should be more frequent IMO but they should also be events!

I used to think that Interior Design was an easy job, not worth paying someone for until I gut renovated my house and suddenly my wife and I had to decide on 1000 little details that I didn't even know existed, all interdependent on each other. 

Our pest management company traps (snap traps) on the interior and baits (poison bait boxes) on the exterior.

Just a couple photos of the outside building so I don't know the interior condition of the property.