Financing complete, mortgage registered, but no house construction

If the situation allows it, selling the house without major losses would definitely be worth considering, or even better, doing it in advance.

But the "construction stress"... oh dear... I really wouldn't feel like dealing with that :)

Well, the stress can potentially be compensated with a lot more money. I would soberly just make it dependent on the expected sale price. If something can be gained from it, then the work would be worth it to me. Although I don't see the "work" as that dramatic either, because you probably wouldn't be as engaged if it's not for yourself ;)

Why are you actually asking? That surely doesn't apply to you yourselves, right? You are already building..

If the situation allows it, selling the house without major losses would certainly be worth considering, or rather, starting early would even be more sensible.

What speculation is. It can backfire. And it means work in any case. Speculation can also be taxable.

I am of the opinion that a new build is like a car: 20% off from the lot. Why? For example, you build for 500k + 20k incidental costs = 520k and want this back from the buyer. He has to pay a total of 565k because of the incidental costs that then apply to him. Over 10% more than the construction cost of the building + land. For a house that is more expensive than building a new one yourself. What do you think the buyer’s bank will say about that, which will calculate the lending value? Furthermore, I would be very aggressive as a potential buyer in such an offer, as I would assume a forced sale. And an early repayment penalty at my own bank will still be due. Plus all the risks that house construction itself entails.

The prepayment penalty will definitely apply. Whether before or after the construction. So at least that part is not saved. And today, given the interest rate development during the construction period, that could have been a good or bad decision.

In addition, you will have to pay taxes on the proceeds. There is a ten-year period. Unless you have lived in it yourself for the last three years.