Land and home financing - together or separately?

then also from the developer (who also wants to make a little profit).

Misunderstanding: we are building with the developer, not the OP ;) Otherwise, I fully agree with you.

We are planning to get a few offers from prefab house providers such as Weberhaus and then also make an approximate calculation of what a solid construction and self-contracted work would cost. Although with the latter, the 40-efficiency house would probably be off the table.

Self-performance might also be possible to some extent; you just have to look at the subsidies again. With Weberhaus, the technical package alone would already be sufficient for us. My father is retiring soon and can help here. He built his own house 15 years ago and did the interior work quite well himself.

Let's see if our Ministry of Construction will still make changes to the KFW subsidy. The loan of up to 190,000€ would also be interesting.

What concerns us now above all is how we finance best. Finance the plot as the first variable?

Have you ever calculated a rate? With normal interest rates, it would be well beyond €3,000/month – if you want to manage that in the first year, you have to use equity, which in turn drives up the loan amount.

Building smaller (why 170sqm for three people – that could easily be 20-30sqm smaller?) would make it much more manageable.

The financing of the property ultimately depends on the house construction and its financing, at least strategically. Therefore, you should be clear about what kind of house you can actually afford. Unfortunately, due to lack of experience and expertise, I cannot give you any meaningful concrete advice, as our situation is different.

The rate should be around €3100-3300 with 2% repayment of the bank loan. With KFW and WI Bank, there is a repayment-free period, which can possibly be used until the child starts kindergarten. My wife actually wants to get back to 100% as quickly as possible and has mid-term chances to earn over €100k. And even if not, €4000 net should be enough for a good life.