We are deflating "Vapor" paper.

I prefer no padding under vinyl plank flooring, but some people will put a very think pad/vapor barrier underneath

No further need for further vapor diffusion resistance. 

Vapor barriers?

New ceiling in carportInspector suggested some vapor barrier in the crawlspace of one building.new railing on balconiessome new appliances and water heatersNew laundry machinesAt the end of the day, I am still learning, but I am struggling to see what to do to make this thing profitable. 

Is there a vapor barrier under the floor or is it just on the bare concrete?

While many middle-men were vaporized by that internet phenomenon; travel brokers, traders, insurance, etc., Realtors® and mortgage brokers have gone unscathed thus far.

Ideally, you would now prime the wall with two coats of oil-based primer like Kilz Original while wearing a respirator equipped with organic vapor cartridgessIf that doesn't work, the plaster or drywall has to be replaced, with all the mess and expense involved.

Slab vapor barriers can be problematic. 

May very easily have nothing to do with a "leak".Concrete is porous, and air, water, water vapor, etc., will travel through it.