The property must of had some leak.. right now on the floor is a sound deadeding underlinement, that seems moist..

Ever since a competitors sales Rep told me on the side that it was the best and their pigment count was through the roof...I have never been disappointed!

People have to remember to clean them and put water in them.I’d be concerned that warm moist air is being blown inside the unit.

I'm installer of user of direct vent fan with humidistat. vent heavier moist air near floor, and replaced by air exchanges min 3 per pp x day. installed $1500-$2500 vents  aprox 2000-4000 sft. depends on region and avg humidity levels. a whole active not passive cs basement vent 230cfm more. installed into wall is vent like #1,  with 3-4 manufacturer's in no.

It is extremely moist down there and we have had a stretch of 90 plus degree weather with extreme humidity the last 2 weeks so we are now worried about mold.

It would take you approx 13.5 Months to overcome the loss of one month rent PLUS you will moist definitely have some fix-up / make ready expenses if these folks move out. 

I would not require any structural improvements to the slab at this time, but I would recommend the owner maintain the following items in the future:Maintain grading around the foundation of the house per the attached specificationsKeep soil near the foundation walls moist during dry weatherExpect cracking in floor, and seal with flexible sealant when visibleThe proposed maintenance is designed to retain strength of the foundation.

@Michelle BrightThat "silver coating" is an aluminium pigmented asphalt which is rolled {painted} onto an modified bitumen roof.  

We had a buyer mold inspection last week and their was no more mold found than is reasonably expected in a moist climate.As long as you budget for addressing the "cause" and not just the symptom you'll be fine.Alternatively, you could just market the property to microbiologists as a test lab facility.. maybe not.TTFN,Greg

(radiant floor heat is absolutely not in the budget)I personally abhor carpet, and I'm sick of laminate plus it may get moist.