Building a house financially feasible or a pipe dream?

Well, we simply need that much space with seven people.

The granny flat for the parents should definitely be 80m²; I don't think much less is feasible.
The apartment for us, with three children's rooms, can hardly be smaller than 140m².

What might be possible is to convert the attic into a study, have no basement, and instead have a larger garage + utility room, plus quite a bit of DIY work.

What might also save money, but can cost nerves, is taking the awarding of trades into your own hands – my father has many good connections with companies and also a lot of knowledge and expertise in such matters – he could surely coordinate that well together with an architect.

I agree with .
As of now, we come to approximately 335k for 134 living space plus basement (house costs only + equipment).

What exactly are we talking about with these costs?

Is that then "turnkey" including everything? What is included in these figures, what else comes on top?

Land and incidental construction costs come on top, that's clear. Costs for bank and notary etc. also clear. But otherwise?

Do your parents still work? Or are they low-income, so they can't pay rent or increase the equity? Hardly anyone can afford to finance two apartments... even if they love each other

What exactly are we talking about with these costs?

House, bare without floors and wallpapers. Without lamps, without kitchen.

Both parents are retired with relatively low pensions. Equity is practically nonexistent.

They don’t pay rent, that was agreed upon back then. In return, I bought the house only through "sham contracts" for €90,000. From that, the remaining debt on it was paid off, my car was paid for, a vacation was financed, and a few other things – they really didn’t get any money for the house, just the lifelong right to live there.

If I build new and sell the old house, they have to come along – that’s what I want. I don’t want to put tenants into the old house for them (that wouldn’t be financially feasible anyway), nor can I throw them out on the street. The only conceivable thing would be their own condominium, but they certainly wouldn’t be thrilled about that, and I couldn’t do it either...

Besides, the condominium would also cost money.