We expect costs for the house including the floor slab of up to approximately €400,000.
For what size? That is already relatively tight. There’s really no money left for a basement. But, you must not only look at the invoice for the house in the whole story, but consider the property and house together, including the planned outdoor facilities.
Our plot has a similar slope (2m diagonally across, about 70cm of that in the building area). The house digs in slightly at one corner and comes out at the other. The adjoining terrace amplifies that and extends quite a bit further. You also don’t really have much space to terrace down, especially towards the rear access road. It can be that you have to support not only the soil but also part of the house. I would definitely not decide anything here without once reasonably calculating the necessary work for the outdoor facilities.