Is house construction only possible with funding from KfW and the Landesbank?

An apartment is planned so that the slope can be used as a basement and apartment, making it perhaps more affordable through rental income.

If the property’s slope necessitates a basement, a residential basement is not only suitable for renting out. That would be my "Plan A" to consider in my own space planning. Playing landlord with a batch size of one housing unit is not attractive, and the subsidy benefit for an apartment is often a net zero-sum game.

A granny flat is planned so that the slope is used as a basement and granny flat, making it perhaps more bearable through the rental income.

Again: you have to be able to afford a granny flat. These are additional costs compared to a house with only one dwelling unit. Such costs can hardly be covered 100% by subsidies. It usually doesn’t work the other way around: building something you can’t afford and then thinking that the rent will cover the payment. If the salary is tight on top of that, even less so. You also have to pay taxes and, if applicable, already consider everything separately in the planning and arrange it financially (at least when subsidies are involved). Whoever has a sloped plot and actually cannot afford a basement financially plans a livable basement instead, and then their second level on the ground floor. All just for themselves instead of giving the tenant the garden part and having to take the tenant into account. Or do you feel like living around your tenant including a parking space in the front yard and experiencing a financial fiasco—despite rent?

Thank you for this information. May I ask what your monthly rate is (40% of the net household income?) A granny flat is planned so that the slope can be used as a basement and a granny flat, making it perhaps more manageable through rental income.

The rate is about 1631 euros, which is 34% of our income. We are 32 and 34 years old and have a term of 30 years. When we concluded the financing, both of us already had tariff increases scheduled for the end of 2024. For us personally, with two children, 35% would have also been the maximum acceptable.

Some banks are already doing that. We completed our financing in March through Interhyp with a regional savings bank. It consists solely of KfW and NRW.Bank loans. Brokers like Interhyp or Dr. Klein could certainly help to mediate with a bank that offers such a construct.

Same here for us. The regional Volksbank exclusively brokered funding loans for us with KFW "300" and NRW.Bank "sustainable living." According to the banker, one is currently glad to be able to realize any viable real estate financing at all.