ServPro quoted $3000 to have his items moved into a pod while work is done and to have his items moved back, but he refuses to pay a penny for anything (including rent for a year and a half I might add).To make matters worse, he threatened to unplug all water mitigation equipment left running in the condo used to remove moisture and possible contaminants from the air.

And depending on the amount of contaminated water flowing into the concrete, and the composition of the concrete itself--fillered or not fillered--mold could grow in the concrete.

I once was required to remove the top 6 inches of dirt from a 50 x 100 foot lot (asbestos contamination complaint from the clean air division of the Dept of Ecology).

Moisture and other contaminants that can get into a refrigerant system, if its not evacuated properly can severely shorten the life of a compressor.Typical condenser costs 1,000 or so and proper install can be 6 to 8 hours depending on the system conditions.  

A lot of that will depend on your state's particular laws - both on how a non-leaking tank is to be decommissioned and how a leaking tank is handled.If there is a leak, now is the time to find out, and possibly back out of the deal, even if you sacrifice your EMD.Here in MA, someone who buys a contaminated property acquires the responsibility for cleanup. 

Black mold is like any other household growth/contamination...it doesn't come back unless the conditions that caused it come back...did the remediation company give you a certificate or warranty?

Opening a kitchen window painted with LBP, for instance, while preparing food could cause lead contamination.

Area and neighborhood are great but always rumors the area wells have had contamination in past years.

Contaminated soil, lead based paint is still used commercially, just not residentially, high levels of radiation, mold, asbestos. 

Unfortunately, no banks will loan money on the property because the land is contaminated.