Slope at the farm entrance?

If it can be avoided, I wouldn’t build it.

At my parents’ place, the steepest spot has about a 25% incline.
Ok, the driveway to the garages isn’t standard anyway.
At the highest point about 25%, at the lowest 5 or 6%.
With my car, I can only get to one side in front of the garage driveway without scraping.
My father has been annoyed for over 30 years that he didn’t get approval to build the garage lower. He wanted to build it 50 or 60 cm lower, which would have made things a lot easier and made the stairs to the front door even longer.

My in-laws have about a 20% incline.

Only children enjoy such inclines in winter.

Unfortunately, there is just no flat ground here.

And the garage at ground floor level?

That is not always so simple. As a rule, it throws the entire planning and concept overboard.

Then it's just a bad concept for this plot.

That’s not always that simple. Usually, it throws the entire planning and concept overboard.

So what? If he’s already thinking about it himself and is unsure, then you should throw the entire planning overboard and start anew. Instead of being annoyed for a lifetime. Building a house is generally not easy.

Yes, building a house means making compromises. The bigger the compromises, the more painful.

I don’t know where the OP is at now, maybe already has a building permit?