By the looks of it i would say your Dad is right, it looks like the concrete has deteriorated due to water. you do not need a foundation co. just hire a mason to cement it back up inside, but first take care of the cause on the outside, get that leader pipe to drain away from the house by either extending the pipe above ground or dig a shallow trench and run a pipe under ground away from the house. also make sure the soil around the house is pitched away so that water moves away from the house.

Soils Report.Is there a street?

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.  

Sorry I have not gotten back to you sooner.I am back on US soil now and will call you later this week.

There was a house built on the land in the late 60s, but it was demolished a few years ago because of foundation issues attributed to the underlying soil.The Township says that they know there are "soil issues" with the property, but they won't say how they know this.

 Some progress pics.Fireplace was removed, I had decided to reface it, but upon demo sheetrock underneath was damaged.This added about 4X8 to the  room!

Things like fungus damage of the subfloor, support posts in the crawlspace in soil contact, hairline cracks, and (scariest to me) no foundation on a portion of the structure though majority is pier and block.  

That means the home owners are not getting chattel loans but a mortgage loan because they are also either:Buying the ground directly underneath the home;or, they are buying a common interest in all the ground.Those types of loans should only be made by an experienced lender who have some type of operational agreement with the community and the management company.Resident owner communities often sound like a very good deal for the residents, but more often than not, they would have been better off if the community was owned by a for profit landlord.

A black glove with a middle finger showing and a nailed up note with the tenants name underneath, KKK Neighborhood Watch notices, couple of n****r messages, and the oldy but goldy, a noose in the front yard.Our tenant calls the cops, and absolutely nothing happens apart from the neighbor being told that if he fires his gun outside again he'll be arrested.Over the next few months this continues.

On the surface it was great, but then we started finding out what was underneath.