The reasoning is that you've created a 2nd vapor barrier that creates moisture that has nowhere to go other than into the roof panels and as a consequence gives you rot which will have to be dealt with 10-15 years down the road.

I agree, have the unit checked out,  moisture is somehow not venting out properly, A/C units, bath fans, vents or maybe you just need to add extra vents so the moisture can escape faster. the air needs to circulate and whatever is causing the issue, it's is close to the area where the mold is appearing,You handled the situation correctly the first time, I'd check with the company that did the work prior and see what their take is.

Tenant agrees to allow Landlord timely access to premises to do maintenance and repair.Tenant will notify Landlord in a timely manner of any damages or problems as they arise, including damages caused by Tenant, malfunction of appliances or fixtures, and water/moisture leaks and spots.Tenant will take care of the premises, keeping them clean and clear of debris.

I have my home inspection and termite/moisture inspection tomorrow afternoon and will be getting the official mortgage documents in order as soon as the inspections both satisfy me.I will be getting a conventional bank mortgage at 5.25% with 20% down and 2 points.

Mold will not grow if you have the moisture in control, it needs moisture to continue to live.

One contractor said moisture is coming through a hole in the exterior stucco, but another said no way because the vapor barrier would block it. 1st one recommended installing insulation, but I've also read this can increase condensation problems.

This property is vacant and winterized, but there is so much moisture in the basement, the water is actively condensing and dripping off the fluorescent light tubes.

Hi @James GreenYou should rent a dehumidifier for a few days and get the moisture out of the air.Also, seal off the basement doorway with plastic so there's no way for potential mold affect your tenants.And finally, this is going to happen again, you want to solve the issue.Best to you.

Every part of the country has drastically different challenges- higher /lower taxes or insurance, moisture issues, mold, etc, so details will help.

Tell your remediator that your goal is to find the source of moisture.