Construction prices are not rising just because there are suddenly different regulations. Our KFW70 house (contract signed in 2012) is still cheaper compared to current standard houses, but not necessarily worse.
If you can save 20%-25% equity in 3-4 years, you are right. But if you save that quickly (even though you rent), according to Vanben’s calculations, it is worth saving. With such a saving rate, the interest rate drops very strongly over the period due to a better loan-to-value ratio. As written, your argument is "pro-equity." It is more about when you have to save for equity longer or are financially weaker. And then part of the increase also comes from regulations; with little money, you are more likely to build according to the energy saving ordinance and not an especially expensive KfW house.
We also had the typical approx. 20% equity. Due to delays in construction, it was probably even over 25% in the end. I also would not have wanted to build without equity. Nevertheless, I can understand the point of the calculation.
Of course. But take a look at all the results of the calculation. With the assumptions Vanben makes, it is definitely monetarily worthwhile to have some equity. So we actually all agree on that.
The only question is from which percentage amount of total costs it no longer pays to save further. And at this point the calculations are of course shaky, because the results are numerically unstable, i.e., small changes in assumptions alter the monetarily most effective equity ratio, so the optimal ratio is highly individual and can only be reliably determined with a functioning crystal ball (future development!). Important and still not considered at all are the
non-monetary aspects, which still do not appear in the calculations. And it makes no sense to keep referring back to the calculation.
The effect of the calculation by is even stronger when children are on the way. Then one may have to move, need money again for moving and furniture because the old ones no longer fit, rent increases, etc. All this would push the house construction further and further back.
That is quite speculation. If you needed that much more money with children, you would also need the same money if you had built. If you have already built without equity and have to cover a high monthly rate, that can possibly become critical. At least in "my world," the stork does not surprisingly bring children, especially when planning to build a house; they come very planned (in our desired year and month...). If children came unplanned, it would be even worse if you already have a house—does the planning (room program, etc.) even fit then? Can you still afford the loan and costs?