That means he will likely have plausible deniability for the damage, as he can just claim that his contractors did the make-ready and never informed him of any mold/moisture issues.

If the bottom of the pile has organic matter or household chemicals or anything with moisture, it's most likely damaging the flooring and walls and attracting pests.

The next item on the checklist is the possibility of moisture intrusion through these cracks.

Like electrical, plumbing, and dangerous chemicals.Also while contractors are okay at generating bids, are they going to be testing for moisture in the walls?  

I'm not familiar with Allure flooring, but if it's practically water proof as noted by @Edward Mccracken, then, as he indicated, the moisture is likely collecting from below the sub-flooring (be it a crawl space, basement or sleepers on a slab) and building up underneath the Allure (e.g., waterproof = impermeable).There doesn't need to be visible standing water for this to happen either.  

Bathroom not bad needs exhaust fan broken n u can start see dots of mold from moisture. 

A couple houses that I've had with vinyl replacement windows have had vacuum leaks between the panes and have clouded up with moisture between the glass. 

Now, you might ask me, “Vinney, I would like to actually have all my students take an excel worksheet and write down the area they’re going to penetrate and also the broker’s name, their phone number, their e-mail in the next column, and then the brokerage house, realty house that they belong to and then you put ten different columns: first contact, second contact third contact, fourth contact, fifth contact.

There are lots of videos on YouTube that will outline the most important part - water penetration prevention.In your neck of the woods, window frame construction material is a toss-up.

Mold appears to be limited to drywall in a couple areas (wall behind a shower that was leaking and has been repaired, wall behind the washing machine).If remediation is $5k for a small job (pulling that out of the air), I doubt seasoned flippers routinely have this professionally remediated, especially when simply tearing out drywall/replacing/wiping down with bleach after correcting the moisture problem is sufficient to correct it.