Construction costs are currently skyrocketing

So ING didn’t do it for me either, although it would have been legally possible. I just didn’t have time for the legal process.

So ING didn't do it with me, even though it would have been legally possible.

What other reason is there besides selling the house? Utilization of the property otherwise not possible, but that's a tightrope walk.

After 10 years refinancing is still possible. We are coming from 4-6% interest rates and it will at least end up there again.

That doesn't make sense. They are paying 4% now while your expectation is 4-6% in the long term. But they are destroying the repayment; with 30 years, the repayment will easily drop by a third with the small percentage increase. With the 10-year term, they could probably refinance at 6% without making a loss. What is the initial repayment rate of the financing? And the idea of taking a long term and then hoping for lower interest rates in 10 years... that's just money wasted, especially when coming from a low-interest phase.

And on the topic of construction costs... we were at the kitchen manufacturer today. Electrical appliances will increase by 12% in May, the fourth time this year. The kitchen furniture has the current price until the end of May, but only if the kitchen is accepted by mid-October. After that, it will go up by 8%...

And the idea of choosing a long term and then hoping for lower interest rates in 10 years... that is simply money wasted, especially when coming from a low interest rate phase.

The tighter a financing is, the longer the term must be in order to prevent an interest rate increase from toppling the whole structure. 20 years instead of 10 years only makes a difference of 0.6%, whereas interest rates could still rise by more than 0.6%. That's the principle. Well, the example in question here has a high premium for 30 years at 105% loan-to-value ratio. But maybe still not the worst idea, since no equity was available and perhaps can or should never be built up. The funny thing is, with 4% interest and 1.5% repayment, you are still done with the loan in 32 years. Higher interest rates lead to shorter terms with the same repayment rate.

As tight as financing is, the longer the term must be chosen so that an interest rate increase does not topple the whole structure. 20 years instead of 10 years only makes a difference of 0.6%, whereas interest rates could still rise more than 0.6%. That's the principle.

Well, the example in question here has a high surcharge for 30 years at 105% loan-to-value. But perhaps still not the worst idea, since no equity was available and maybe never can or should be built up. The funny thing is, with 4% interest, even with 1.5% repayment, you are done with the loan in 32 years. Higher interest rates lead to shorter terms at the same repayment rate.
In 32 years.
I financed an industrial hall when I was 16 years old at 10.4% interest.
I was finished after 4.5 years.

32 years is supposed to be short? We all grow older, but old Finn, this is not just a feeling - half a lifetime.