Financing a single-family house approx. 450k - How to implement?

You know apples and pears, right? When I talk about a double garage, it costs 35,000 compared to a single garage costing 7,000. It's the same with houses, so you are right, a flat rate doesn't make sense.

Yes, of course. But it shows that it is indeed possible to build a house for under 300,000. Sure, it's not a castle, but it's not the worst junk either.

I am repeating myself, but a management consultant does not build a house with wallpaper, laminate, or similar. I do not believe that I made a bad deal. I know the prices from many acquaintances, and new single-family houses in existing buildings are not available here for under 700,000 euros (absolute entry level!) neither in the countryside nor in the city. Living in an expensive spot, but I am glad if it is cheaper for you.

You are of course right. Junior management consultants appropriately play in children's rooms with exposed concrete walls.

I’m repeating myself, but a management consultant doesn’t build a house with wallpaper, laminate, or the like.

I don’t believe I made a bad deal. I know the prices from many acquaintances and new single-family homes in existing buildings here can’t be had for under 700,000 euros (absolute entry-level!) neither in the countryside nor in the city.

Living in an expensive area, but I’m glad it’s cheaper for you

I repeat ... what’s so bad about laminate? I’m going to shock you now. I earn more than many a management consultant and we have laminate.
My child has wallpaper in their room and our place didn’t cost 450k € with everything included.

Really likeable box thinking. Welcome to 2018

Honestly, now a discussion about laminate? I'm laughing my head off here, but well, a little fun has to be..please use a search engine to find out why laminate has no place in a single-family house, unless you have to build cheaply.