if its ground water its presumably just in the basement. 

Personally, I don't like buying property with major fire damage, or properties that have groundwater intrusion issues that can't be easily fixed by downspout re-routing and/or grading. 

What would you do if your well went bad and the groundwater became contaminated?

You've been sharing groundwater with a neighbor for years. 

It would be nice to find out if there is an ongoing issue, soil issue, ground water issue, etc. prior to making a final decision.Kind regards,Arpad 

Depending on the well, it's depth, age and a million other factors, contamination.If it's an old hand dug well, beware, cause you'll be drinking groundwater.

Do not buy the property until that tank has been inspected, decommissioned and removed (and any soil or groundwater contamination cleaned up / remediated).TRUISM: If there's an underground oil tank, and it's steel, it leaked.

Actually, house is sitting very close to the ground water level and nobody knows where the septic is located.

Especially to replenish groundwater.5.

Areas with more senior water rights will probably fare better and areas that rely on groundwater (Pinal County and many of the newer developments that don't get allocations from CAP) may fare worse, assuming current water rights remain in place and play a role.