Contaminated land.

I'll guarantee you that it's contaminated.

I can't imagine you'd want to take it as-is with the tank, because if you try to remove it after buying and find the soil is contaminated, and possibly contaminated the ground water, you could be looking at a bank-breaker of a job.  

For example, if the sewer system backs up are you going to tear out contaminated materials or will you want to try to clean them and "save money" (not recommended).

If you aren't afraid of the soil or groundwater being contaminated from chemicals that were spilled or dumped onto the land, or disposed of in a septic system, then it sounds like the deal of the century. 

You've really contaminated my mind J. ;) That was the reason why I got a Tesla.

The dry cleaner in the adjacent shopping center has been dumping perk in the rear of the shopping center for years and the contamination has reached the subject property21.

Jobs seemed to be made by professionals as removed walls contaminated with black mold and gave them the right treatments, but nobody knows who it was, no one knows where the cabinets go and all the stuff inside the property like dishwasher refrigerator etc.

Costs of a large 200 Contaminants kit cost less then 1st check to a lawyer.http://digitalstarlight.com/iot/water-quality-testing/

Sometimes a lender will accept that.You could put as a condition in the contract that seller is to pay for a phase one report on behalf of the borrower and the borrower gets to choose the engineering firm to complete the report.Have you checked the EPA site to see if this is known to be close to a contaminated area already??