Building a house at 21 years old .. too young?

That by no means means to me that I shouldn’t strive for a 100% solution.

Oh yes, Pareto does not mean a plea to declare 80% as the new benchmark – but merely an awareness that the mountain beyond the Pareto optimal point becomes many times steeper; and – and that is what I wanted to make clear: if you pause at the 80% point with this insight in mind, you still have the energy to reach the 80% point of the second project again. Alternatively allocating the same energy to bring the first project to the maximum point might be wise at sixty, somewhat at forty, and at twenty rather not the wiser choice at a 50/50 fork.
My advice – but that’s precisely why so many of us here have such different views, so no one has to take my advice as the only option for lack of choice – in this situation is: weigh carefully and dose sparingly how much optimization should still be invested in house one.
Yes, it is entirely justified to doubt that it would come as surely as amen in church if I consider it likely that the OP a) will fare better with "learning house now, permanent house later" and b) will still be ready to make the leap to the second stage under 30.

A house for eternity? Yes!!! Why not?

Because life and the development of our society will very likely hold many surprises for people who are now in their early 20s. Our world is developing increasingly disruptively. Of course, you can still give your all for the first house and fully commit yourself. Acting sustainably is perfectly fine. Even in your early 20s. Associating a concept of eternity with it is not sustainable thinking, but rather naive.

Since the appointment is in November, there’s no need to dissect the floor plan now. That would only spoil his anticipation. And it’s not that bad anyway. Look forward to your house and be creative in using the space wisely.

Yes, the hallway is small. You just have to be creative. Shoes go under the stairs and hooks for jackets above. What’s too much goes into the closet in the office. There are worse things.

The kitchen/living area isn’t spacious, yeah... so there’s just a 1.5m table. You can always extend it when guests come, and then it’s just a bit tighter for one evening.

Sure, some things could be nicer, but when I see the houses of my relatives, this floor plan is pretty much an improvement over the existing buildings. Still, no one is unhappy.

We were also advised not to plan the living area as a passage to the kitchen. We still love it that way. It just has to fit the family. But you’ll only find out later.

And don’t worry because you’re still young. I met my wife at 15 and even at 32 I don’t think about swapping her out. If you’re sure... go for it... There’s a solution for everything.

You just have to make compromises in some things. I think 80/20 is right for the office to manage the workload somewhat, but it’s not part of one’s own four walls. If I were to put in Pareto-spackling on my ceiling... it would look awful and I would get annoyed every time I enter the room. 80/20, yes, but only where it really makes sense for you.

And if you put in effort now, it will also be easier to sell later if you ever look for something different.

Shoes under the stairs

No, that's the pantry!

What speaks against dividing the area under the stairs so that I use the part that is sensibly usable from the kitchen and use the part from the hallway that is not suitable for the pantry? A few shoes/boots should go there. Depending on how much space there is, maybe even a shelf for a second level for the shoes. Above, on the stairs, a few hooks for the jackets.

The OP now just has to come up with clever detailed solutions for points that the floor plan itself does not optimally solve.

I personally have no doubt that with the floor plan (despite the undeniable deficiencies) you get a house in which you can live wonderfully with clever use of space. Even with 2 kids.

South-facing rooms are not always a blessing either. We built 3 children's rooms. And I have to say: the north-facing children's room is the nicest because the evening/afternoon sun shines in wonderfully from the side and there is a large skylight where you can place the bed underneath.