Hmm, financing is really tough. Maybe you should take a look at the catalogs of the "budget providers" after all. We built a spacious bungalow with Heinz von Heiden and are very happy there. And at a price that makes others drool. We didn't excessively save on the equipment. But it was not the heating system with all the bells and whistles, but a simple heat pump, ventilation system, etc. Maybe then forgo the KfW standard (which also saves a lot). Then no basement, but an attic with a hatch (we are still young) and a sufficiently large shed in the garden. We paid a total of 430k for our project (including bungalow (189 sqm), garage, carport, plot (123k), filling, groundworks (which were very expensive for us)). Our monthly repayment is 1400 €. I am currently struggling a lot and will go on parental leave starting January. We have one child. We completely finance the construction from my income, including all other payments like daycare, fees, ancillary costs, etc.