Buy land and build

Soil reports usually also contain recommendations. There is certainly something about additional effort or necessary soil replacement. Clayey soil is usually not so nice

But that is just a guess that one exists.
I am assuming a general construction report (also a guess ;)) for the entire area... but as I already wrote above:

I and the others also reluctantly write novels on a whim...

Cohesive soil types here suggest clay... More precise information will only be available after the soil survey. Apparently, water-bearing layers were encountered during the excavation of the sewer channels... Fortunately, a groundwater level did not appear. Thanks for the exchange so far. More precise and targeted questions I will then ask after the purchase!