It's usually from downspouts not extending far enough away from the house, pour grading and especially concrete driveways that slope towards the house, or sometimes a crack in the foundation.

What is the difference between a concrete home and a block one...

The one thing that makes me a bit nervous is that the outer walls are built of concrete blocks and that does not seem to be very common around here. 

Also, have any installed in a concrete basement floor that wasn't 100% leveled?

There are also signs of a cover up at the base of the foundation because there are new concrete blocks there to hide the foundation and a temporary drain placed nearby to prevent water from reaching the foundation.

Now you have something concrete to present to the sellers.  

But if you pursue this, demand that ALL mold items be removed and replaced--sheetrock, studs, grout, concrete, insulation, wood, whatever.

You can also use concrete to encapsulate the ground in a crawl space and then install a sub slab depressurization system, aka radon abatement fan.

Assuming a 4" concrete slab for floor and a 1/2" of gyp board for the ceiling that would effectively give me a height of 8' 1/2" which acceptably checks that box.

The innocent tenant car was pushed over the concrete parking stop and through the cement wall out of the yard.