Raising the property by 2 meters - experiences?

A basement usually costs around 60,000 euros for a single-family house.
Therefore, the filling can already be worthwhile.
There are additional costs such as plastering, sealing, insulation, windows, ceiling, etc.

But here he would have the benefit of the granny flat. He could offset this.

Then of course there are more costs if it becomes a [Einliegerwohnung]: bathroom, kitchen, more windows, front door, etc. Everything has to be calculated precisely. Also the tax advantages. Whether it is worthwhile depends on the individual case.

The costs for interception are added for refilling

So if I want to have a granny flat and the plot is already 2m below street level, then the basement would be the ideal building structure for it! If the drainage is well planned and the basement is waterproof, then it should work. What about the surrounding houses - are basements "common" here or rather not?

Is there a soil survey available?