Financing question for our construction project

That can work, but it doesn't have to, since with the "small ones" you first repay the cheap loans. If the interest rate hasn't risen dramatically after 10 years, repaying the long loan would have been more sensible. Both options are a bet, one against, the other on rising interest rates. The middle way is then the option that most people currently take. 10 years KFW, the rest in longer terms.

That can work, but doesn't have to, since with the "smaller ones" you first repay the cheap loans. If the interest rate hasn't risen dramatically after 10 years, repaying the long loan would have been more sensible. Both options are a bet, one against, the other for rising interest rates. The middle way is then the option most people currently take. 10 years KFW, the rest in longer terms.

Every financing is a bet. I personally have bet on the continuation of the proven past. In 10 years we will all see whether it is red, black, or green zero :D. Let’s see who will act then :)

I also have 50k Euros interest-only for 10 years in the KFW loan, for which I repay the remaining loan at a higher rate. This way, I reduce the loan with the higher interest rate faster, saving interest and compound interest. However, our total debt after 10 years is so low that I do not worry much about refinancing. Besides, if I were already repaying the KFW loan now, I would have a larger remaining debt after 10 years with the same total rate.

That can work, but it doesn’t have to, since with the "small ones" you first repay the cheap loans. If the interest rate hasn’t risen dramatically after 10 years, repaying the long loan would have been more sensible. Both variants are a bet, one against, the other on rising interest rates. The middle ground is then the variant that most currently go for. 10 years KFW, the rest in longer terms.

That clearly shows that you can’t have it all. Interest rate security, lowest costs, and flexibility. You have to choose one point and optimize the financing accordingly.

The original poster said he wants flexibility. So keep the rate as low as possible (meaning minimum repayment) and agree on special repayments. That is the basis of flexibility. Of course, you can still improve a lot more, with the distribution of special payments and where you could get the money from, etc.