Another issue I have is once you penetrate this skin on the foam it no longer has the vapor barrier qualities and the foam will become saturated and hold water.

I would want to dig at one or two corners down say at least 12" to see what that look like, drill a few holes, moisture test some spots inside and outside...I say go to the city and look up past permits, do they show foundation repairs, if so call up the contractors and inquire.

Source of moisture is identified and eliminated. 2.

One more thought; in my last deal negotiations I was bidding against 3 other cash buyers, my max price was 75k, but I ended up accepting the sellers counter for 80k just to beat out the other buyers, then I did a moisture inspection, found some water damage and was able to get a 10k repair estimate which I used to get the sellers to give me a 5k price reduction to 75k (I already knew there was moisture, and was already planning the rehab anyway so this was really just a bluff to get a price reduction) .

If the conditions that encourage mold to breed exist (moisture mostly) then it will come back.

Fix any moisture leaks, pest control problems, rotting.

Fix any moisture/vent problems2.

Hey @Scott Peters -Dry rot is caused by a moisture/water problem ... we see it a lot around sinks and bathtubs/showers. 

Looking at pictures won't tell you if the HVAC works (or how old it is), won't tell you if the water heater is installed correctly (unless the listing includes pictures of the water heater), won't tell you if there are leaks under the sinks, won't tell you if there is evidence of moisture in the basement, won't tell you if there is mold in the attic, etc. 

its an acrylic based grout that resists water penetration, stains, mildew and mold so it has the benefit of epoxy without the price tag.