Which financing is realistic?

Ok I recalculated

160 sqm x 2000 euros base price
= 320,000 house and furniture
+ 50,000 basement
+ 50,000 construction incidental costs
+ 35,000 garage (masonry double garage)
+ 20,000 outdoor facilities (driveway and terrace)
+ 10,000 kitchen

= 485,000 euros

Due to the hillside location, it may not be much more expensive with the basement, so it may not save enough to leave it out

ETW yes is of course an argument
We thought that in the long run it makes more sense to keep it as additional income but you are probably right

That sounds like a reasonable calculation to me now.
Planable as a starting point.

I understand what you mean about holding the condominium. But it's a very difficult calculation. For what you use less equity, you pay interest to the bank on the other side. There has to be a decent rent compared to the value of the apartment for it to make sense. Not to mention that if you don't sell today, you can't financially implement building a house.

How much do you estimate the value of the [ETW]?

Make the outdoor area 40,000 and the kitchen 20,000, then it roughly fits.

Make it 40,000 for the outdoor area and 20,000 for the kitchen, then it roughly fits.

If you only want to do the essentials first (terrace and driveway), in my opinion you don't have to budget 40,000 EUR. The kitchen varies... 10,000 EUR is certainly at the lower end of the range.

Ok with a possible buffer for the kitchen (because to be honest, the kitchen is quite important to me, although our current kitchen is already my dream kitchen bought last year for exactly 9,500 euros so we'll see) I would roughly calculate 500,000. That is of course a lot...

I estimate the condominium around 80,000.

With the recommended 80% of 500,000 it would thus be exactly the 100,000 that we then would have.

Then just take the dream kitchen into the house. You have the floor plan in hand, if the kitchen as it is exactly meets your needs, in my opinion there is nothing against it. It would rather be silly to throw the money out the window. And just because the kitchen is important to you doesn't mean you have to spend a huge amount of money on it. Sure, you won't get leaf gold-covered solid copper fronts under a hand-knotted diamond countertop for 10k, but you can get a nice kitchen with decent appliances in it.