House construction: Prefabricated house or solid house? Experiences Price range

first of all, links are forbidden here. I know that from personal experience. It can quickly lead to account suspension.

Let's calculate backwards.
550,000 €
- 150,000 € land
- 25,000 € exterior facilities
- 15,000 € carport
- 50,000 € ancillary building costs
- 20,000 € furniture/kitchen/lamps
That leaves 290,000 €. I think you can build a 120 sqm house well for that. But not much can go wrong and no additional costs can come to you.

Don't forget. 550,000 € loan at 3% interest means 1,375 € monthly interest. That means you are at 2% repayment with a rate of about 2,300 €.

oh crap, I wasn't aware of that. as I said, I have a condominium that was built in 2016 and is definitely worth 250,000 to 300,000 euros. I'll have to talk to the bank about how all of that works or doesn't work. and then there's the KFW funding, which will significantly reduce the loan from the bank.

If you want to know more, feel free to contact me at "hausbau_2018 at gmx.net" without quotes/spaces, of course. We can gladly go into more depth there.

oh damn, I didn't realize that. as I said, I own a condominium that was built in 2016 and is definitely worth between 250,000 and 300,000 euros. I’ll have to talk to the bank about how all of that works or doesn't. and then there’s the KfW subsidy on top of that, which would significantly reduce the loan from the bank

Never include the KfW. That should rather be seen as extra money. I don’t even know if there’s anything available anymore. If anything, it’s for KfW 40 houses.

I didn't mean the repayment grant now, or did you also not mean that. I am now assuming a budget of 550,000 euros. 550,000 + outstanding debt = 600,000 euros - apartment sale 295,000 euros = 305,000 euros and then split these.. I don't even know how much KfW currently gives, for me back then it was still 50,000 euros .. according to the internet 120,000 to 150,000 euros. so we make a loan at the bank of 305,000 euros - 125,000 (example) = 180,000 and a loan of 120,000 (example) at KfW. I just don't know if that's possible, I only have the appointment at the bank next week

As I said, I still have an outstanding debt of ~50,000 euros on my condominium, of course one could sell it (current value 320,000 euros).

oh damn, I wasn’t aware of that.
as I said, I have a condominium that was built in 2016 and is certainly worth between 250,000 and 300,000 euros. I will have to talk to the bank about how all this will work or not. and then there is the KfW subsidy, which will significantly reduce the loan with the bank.

Before we continue here, the value of the condominium should probably first be really clarified.