Build all required parking spaces, even if they are not needed?

I assume that you at least make a notional division according to [WEG] instead of a real division. Even with three parking spaces (I read the number as a hint at two residential units per semi-detached house), it is common to have only one driveway. From a fire safety perspective, I doubt that it is officially allowed to squeeze through between the car and the front door. There are situations in which a clever architect particularly displays his superiority over a draftsman ;-)

We did not get as far as the offer in our research. But there are garages where you drive in, then the car goes up. Afterwards, a second car can drive in. The problem is that the first car is not accessible. Therefore, it would not have been an option for us. But you don’t actually need this 3rd parking space, if I understood correctly, so it could be considered. The price was quoted to us back then in the four-digit range. It’s just a lift. (So in addition to the normal garage) I would still include the yellow parking space in front of the house as common property. Otherwise, there is the option with earthworks, where the car drives down. Here you can access both cars. The additional costs with earthworks would have been in the five-digit range.

However, I might also buy out the parking space for €30,000. Visitors have enough parking options anyway.

As far as I know, in [Markt Schwaben] you need 3 parking spaces for a single-family house with over 100sqm. Even without a granny flat.

Honestly? If I take the costs for a duplex parker including the necessary power connection as well as the costs for repairs over time, then I would simply pay the €30,000 buyout. Because the duplex parker often only suffices for cars up to 180cm high (I know max. 200cm).

For example, from the market leader Wöhr:

Who is the one on the upper pallet? And that perhaps for €25,000?

It's just a lift. (So in addition to the regular garage) [...] Otherwise, there is also the option with earthworks, where the car goes down.

Why "otherwise" and "option"? - without excavation, the lower car must be driven out to get to the upper car. This only works for real SECOND cars (and for couples who don't mind driving each other's car - and who NEVER leave anything in the car!). Lawyers have a nice word for this: "unrealistic."

For example, from the market leader Wöhr:

Funny drawing. Looks like a machine to flatten the upper car if you park it in first ;-)

Why "otherwise" and "variant"? - without underground construction, the lower car has to drive out in order to reach the upper car. That only works for real SECOND cars (and for couples who don't mind driving each other's cars - and who NEVER leave anything in the car!). Lawyers have a nice word for that: "unrealistic".

But if he doesn't actually need the parking space and this variant costs 5000€, while not building costs 30,000€, then it is the more sensible option for him. For us, it was out of the question due to impracticality. But even with parking spaces behind each other, one always has to drive away first if the other wants to leave. Not much more practical.