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

I am simply damaged by the many mothers of my youth who made up for what was missing at 20 by the end of their 30s.

I no longer have anyone in my circle of friends who got together young. Back then, it was the great love, the first girlfriend/boyfriend; at the latest by 25–28 they wanted to be with others. Unfortunately, that's human nature. I hope you can maintain the house on your own.

I didn’t even mean it that way. Breakups always happen. And yes, no one here is with their teenage sweetheart. My husband and I have known each other since we were 18. But back then, we didn’t particularly like each other.

Many people "break their horns" around 20 - if they don’t, they make up for it later or cry over the supposedly missed opportunity.

Although I’m skeptical because of the age, I’m keeping my fingers crossed for the OP. Every builder needs luck.

I no longer have anyone in my circle of friends who got together young. Back then it was the great love, the first girlfriend/boyfriend, by 25-28 at the latest they wanted to be with others. Unfortunately, that’s just human nature. I hope you can maintain the house on your own.

I don’t think it’s right to draw a general conclusion from that. Of course, the opposite is also true. We have many acquaintances and friends who got together very early and are still happy. We ourselves are also "such people." I think it’s nonsense to say that people inevitably go crazy in their late 20s or mid-30s just because they got together so early.

and still happy

Yes, eternal happiness is quite different when the other is busy or writes hectic and emotionally charged text messages next to me in the parking lot.
No offense (fortunately I haven’t experienced it either), but if you have enough observational skills, you can see the other’s “happiness.”
However, I don’t see that as a focus now either. It’s just that life still offers so much, and there is little time and money left for that after building a house.

To be honest, I would be curious to know how a couple in their early 20s plans their house. My wife and I have also been together since we were 16, but if we had planned a house at 20 - oh dear - I would have already remodeled it today. Of course, this has nothing to do with you, but back then I would have had the wildest ideas: floor plan doesn’t matter! The main thing is that a 100-inch TV fits in the living room! I don’t care about the bathroom but the liquor bar has to be in the basement and EVERY piece of furniture gets LED underlighting!

and soundproofed.

Seriously, whether it's a schnaps bar - later a play kitchen, whether it's a gaming den - later a children's room, rooms can be repurposed. I don't see a problem with that. Especially since the OP seems to be more "down-to-earth" than some others at a young age.