Questions about hillside property

Hello dear forum community.

In "our" new development area (here we are considering building), the plan for the lot division and the street finally came out today.
I am attaching a plan below, where contour lines are also drawn, so you can estimate the slopes well.

Since these are hillside plots, I have a few questions about this:

1. Can one roughly estimate the additional costs for a basement? Due to the slope, significant earthworks are surely required even for a "normal" slab foundation.

2. Is it more sensible to secure a plot above and below the street? Especially regarding sunlight, access to the garden, lift station? etc.?

I see the following advantages and disadvantages:

Above the street:
+ Direct access from the living room to the terrace/garden
+ Garage possibly integrable into the basement
+ Possibly a granny flat (for later)
- No sun on the terrace if it is behind the house (north)
- Terrace facing west means proximity to the neighbor

Below the street:
+ Sun on the terrace
- Possibly a lift station?
- No direct access to the garden possible

Thanks and best regards

just a very brief thing that came to my mind spontaneously:
below the street
- if there should ever be heavy rain and the sewer system can't handle it - where does the water flow to?

just something very brief that came to mind spontaneously:
below the street
- if there should ever be heavy rain and the sewer system can't handle it - where does the water flow?

You also have this problem above the street. Behind your own property, the terrain continues to rise, which means you definitely have to deal with water pressing against your house and need to install drainage in front of or behind the house.

We have the house above the street and also a north-facing garden. I commented on this earlier. Take a look at my posts.
We have the entrance and the garage integrated in the basement and are very satisfied. You can read about the planning in my planning thread. :)

So, we are building below the street, but that is for financial reasons *g*. Fortunately, we do not need a lifting system, but you can see that in the piping plans of the development area, which you can simply request. If the shafts go down deep enough, it fits. What you do need for the basement floor, however, is a backflow prevention system for gray or black water. The latter is used by us and costs an additional €2,500.

But the same can happen to you above the street as well, depending on where the shafts are located for you.

Above the street, you can also have a terrace on the sunny side (assuming the slope faces south). It depends on how far you can embed the house into the slope. However, that means significantly higher costs for excavation.

Conclusion: Both have their advantages and disadvantages. The decisive factors are the location, slope, and development plan to determine whether you can realize your idea. So, you should first consider whether you want the terrace in front of the living room or a balcony. Ground-level access or stairs to the living area. Then you look at the possible plots and the conditions there to be able to say whether what you imagine is feasible there.

Regarding the costs: Yes, they are somewhat higher, but mostly because the room height of the basement is increased and it has to be included in the thermal envelope. What you also have to keep in mind (we are currently experiencing this too) is that the ground can also lead to additional costs because when building on a slope you have to found in different soil layers, and they may not be equally load-bearing --> soil replacement.