However the air was dry, so I found that reassuring.The mold and moisture in the basement was not included in the provided disclosure.My realtor just told me that a contract was accepted on the place, 2 hrs after we looked at it.My thoughts:  Its a good price, and even at asking the cashflow works and provides a $250+ monthly income.  

After the flood we were required to have a moisture test on the studs and certificate prior to closing back up the walls.

In addition to moisture/mold issues, I wanted to add also that if you have any laminate or vinyl plank flooring, the warranty can become useless and flooring damaged if the temperature is not kept at certain levels. 

I've had luck with some thinner varieties but I've had thinner AC4 grade laminate buckle because of moisture.

I have no reason to believe there is any moisture issue from the building itself (and I've had more than one contractor come out, two even that put moisture readers on the walls and ceilings with no abnormal results).My question is, what steps should I take as a landlord?

Any framing against cement walls must be pressure treated, contain moisture barrier, and insulation.

I have seen that many,many times and it is in many cases a cash flow killer.If tenants do not pay or reimburse even they do not report water leaks which can cause higher water bills, mold, water damage to walls and floors, bug infestation from the moisture growth,etc.Tenants also use about 30% plus more resources on average when they are not paying directly.If tenants paid directly and water drips once every 30 minutes from faucet you better believe most will let you know right away!

The water has not been turned on in 1 year so I am unable to see where the leak/moisture could be coming from.  

They also add a lot of moisture to the air and they recommend a window be cracked open.

Moisture getting in through window.