How do I determine the house costs before buying land?

You could build a nice, simple single-family house for 350,000 including house and garage. Outdoor facilities and kitchen not included.

You thought correctly. But the question is what YOU understand by simple and what size it will be. Just take a look at new(er) properties on Immoscout and you will have a good idea of the price.

The construction prices seem to be even worse than I expected. We had actually thought that with €450,000 (including €100,000 land costs plus ancillary costs + €350,000 for the house and garage) we could build a nice, simple single-family home. Exterior landscaping and kitchen not included. But with construction costs of €2,500/sqm, at 150 sqm you are already at almost €380,000. That’s really crazy...

You didn’t write anything about the land, no idea how the prices are with you.

Nice and simple... is relative. In the initial post you mentioned things like electric shutters, heat pump, etc. With the equipment you can influence a lot. There are some here who don’t understand why you would even need shutters, just to name one example.

The region makes a big difference. If you specify a bit more, maybe one or the other user can say something about it.

And the question about the price increases remains open. Currently, 7-10% construction cost increases per year are almost normal. Whether that will continue for the next 4 years - no idea.

You are right, no one knows our idea. We probably don't know it in detail ourselves either. You have many wishes, but you say goodbye to most of them for cost reasons. My actual question, why I wrote the amount here, was more about how to proceed. Buy the land and be surprised in 3 years what the money will be enough for? Or discuss everything thoroughly somewhere beforehand? Without knowing how reliable the costs are? I am for the option to thoroughly chew everything over once, but my friend does not see the reason for it (because of the reasons from the first answer).

I am in favor of thoroughly chewing everything over once, but my boyfriend doesn't see the reason for that (because of the reasons from the first answer)

What does he mean by that? That prices will drop? Or simply that it doesn't make sense because you don't know the prices?

Calculating everything exactly is nonsense. That is clear. But if you have a budget, you should at least roughly estimate whether you can get a house for that budget that meets your expectations.

Depends on whether you live in a rural area or not. We live in a rural area and here you could get the house with a garage built for 350000 - this year. But 300000 would probably be too low. Why don't you build immediately after buying the land?

Buy land and be surprised in 3 years what the money will be enough for?

What is the worst thing that can happen? You break up or the budget no longer fits in 2022. Then you just sell the land again. So what.