Elevator with 2 floors - who has already implemented that?

Let's assume 40k, then better a bungalow and for the 40 a larger plot of land.

Of course, it is easier to simply build a bungalow. But: Unfortunately, it is difficult to find a suitable (= rather large) plot of land that also meets our other conditions. The trend towards denser building is understandably increasing. However, this also leads to the (offered) plots becoming rather smaller. And we do not want to build over almost the entire plot - a garden has to be there. The land issue should be clarified in the next few months (including the development plan): After that, we will look at the possible options. Due to the links and various internet research, it really is the case that an elevator for 2 floors becomes relatively expensive. Therefore, if it is 2 stories, we will probably provide a straight staircase with a metal railing (and wide enough): Then at least the prerequisites for the subsequent installation of a stairlift would be given (then one can also think about the necessary power supply at the same time). If anyone actually has experience with an elevator, I am still grateful for tips, experiences, etc. Thank you.

that an elevator for 2 floors becomes relatively expensive

What is expensive for you?

What do you consider expensive?

For the feature, I already find 20,000€ quite expensive. However, if the elevator actually cost around 10-15k€ when considered in isolation, that would be an option. Moreover, this elevator does not necessarily have to be in a shaft – there are apparently "freestanding" elevators – but I do not know the total costs of those.
Additionally, it was mentioned above that maintenance and the activation of an emergency service are needed: these are not investment costs, but at least operating costs.
Building a bungalow would have the advantage that you could forgo the space-consuming stairs. I will wait to see how the parceling is finalized, how the building plan is ultimately approved, and the (overall) prices for the building land are fixed.

When it comes to implementing a retirement home where one wants to live as long as possible in old age, I assume that children's rooms no longer play a role. In this respect, I would not build in a traditional way, nor necessarily include an elevator in the considerations, but rather focus on creating a barrier-free unit on the ground floor with a bedroom and shower bathroom, and possibly a room with a bathroom upstairs where a caregiver could live. If then crutches, walkers, or even a wheelchair should move into the house, you can spread out downstairs and keep the upper floor free for guests. I imagine that one would feel more comfortable than having to go (be driven) upstairs every day or evening. An elevator with its costs would make sense if there are physically disabled family members during the house planning, or a stairlift in older buildings if the ground floor does not offer a convenient sleeping option.
Best regards in brief

If we build two stories, our considerations were different...
Ground floor: living room (large), dining room, kitchen with pantry, small guest room, shower/WC, utility room, cloakroom.
Upper floor basically "private area": 2 bedrooms (I snore, so everyone has their own bedroom), 1 bathroom with shower / bathtub / double sink, laundry room/ironing room, terrace.
Of course, the rooms could also be planned accordingly in a bungalow. As I said - we are still very much at the beginning. However, we at least know which rooms we want and approximately what size.
The partly conflicting "requirements" still have to be brought into harmony with the structural (and financial) possibilities. We have set the financial framework relatively tight. Due to the long lead and planning time, however, we can proceed much more purposefully and enable the manufacturer (desired supplier: Keitel-Haus) to integrate this into the overall planning in the long term and make necessary decisions in stages.
By the way, this would be my third house construction: so I already have some experience. Therefore, I also appreciate your inputs, hints, and suggestions – they help in conducting discussions (notably also with my wife) and making the decisions that are necessary.