Residential unit in the basement

We are currently planning 2 residential units. A granny flat for my parents. Due to the size of the house, some plots were excluded. However, we might only use one KFW loan because it allows us to realize our desired monthly payment better. You have to repay the KfW loan at a certain percentage. That does not make sense for us, as the rest of the total amount also needs to be financed.

Has construction already started?

We will possibly only take out a KFW loan because it allows us to better realize our desired monthly rate. You have to repay the KfW loan with a certain percentage. That doesn't make sense for us, since the rest of the total volume also has to be financed.

If it fails because of that, you should urgently review your building plans. The term is extremely moderate at 30 years with a repayment rate of 2,x%.

It makes no sense with any loan (also with the bank) to approach it with less repayment.

We might, however, only take out one KfW loan, because that better fits our desired monthly payment. You have to repay the KfW loan at a certain percentage. That doesn’t make sense for us; the rest of the total amount also needs to be financed.

I don’t understand now? We are also planning with 300K KfW, fixed for 20 years, 2 years without repayment, and a 30-year term. The repayment is manageable, especially since we wouldn’t plan for more than 30 years anyway.

So I can understand both sides here... but I wouldn't overstretch the matter too much and only assume bad intentions on the part of the OP.
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In the initial post, second sentence! Only because of the money, I don't want to accuse anything.