Probably because the "construction partner" is less of a partner and more of a company that wants to sell services. Withholding costs before the contract is signed, which are anyway "on the builder's side," is a very common method. Your finishing work also doesn't matter to the construction company. Once you've accepted and paid for the better shell, the deal is done. Whether you then move into a construction site because the money doesn't cover all rooms... they don't really care. We are planning with a similar budget, with less own work and probably better equipment, but we also want to build significantly smaller (120-130 sqm) and our plot doesn't even cost half as much. Still, I'm not sure if I can keep it to 500,000.
Don't forget, you can postpone a lot to later, but then there has to be money for the carport, garden, etc. What monthly payment have you planned and what do you have left to finance such projects? How did you calculate the incidental costs for the new house? Even if it is much more efficient than the old one, with double and triple the size and exterior walls on all sides, heating costs tend not to decrease. Plus things like property tax, insurance, etc., which are significantly lower with an apartment than with a house.
What I really don’t like about you guys is that you have two loans open that wouldn't be necessary. Also the calculation with income and kid costs. That little child benefit goes for the daycare (under 3 is expensive) and you need that if you want to work again. That’s not even counting the stroller, car seat, clothes, etc. I think you underestimate the costs for a child.
Sorry, the daycare has even already been chosen and costs 80€ per month. And precisely because it’s a RU daycare! The "normal" German daycares in Berlin, as far as I have inquired, are free! Regarding baby gear, in my opinion, the forum shouldn’t worry at all—first of all, apart from the fact that strollers, baby items, furniture, car seat, etc. have long been purchased, there will certainly be no cutting back or underestimating the costs that children entail. As I said, we are aware of our saving potential; everything the money went on so far (vacation every month, even short trips; designer clothes, etc.)—for most here unnecessary and hardly imaginable expenses, which we have already been abstaining from for several months now and have come to the conclusion that we can live well without them. In my opinion, one should not dig so deep into their pockets, especially since this is already off-topic and has nothing to do with my question about the Ing-Diba bank. The bank also doesn’t know where the money flows to / has flowed so far. What’s important is that we have realized that it will be different once building the house begins. And this is our conscious and firm decision to give up unnecessary luxury in order to complete the house.
Regarding your statement about the developer – our friends built with the company and are very satisfied, they didn’t have to provide additional financing. I get what you mean, but I don’t understand how prices for contractually agreed services can be increased later if you have a fixed price guarantee? I understand very well that ancillary construction costs can become more expensive depending on soil conditions; or that the builders suddenly have extra wishes during the construction (a few more sockets or whatever) which then increased the costs, but the contractually agreed = where do additional costs arise for us afterward?