Should I finalize construction financing now or wait, experiences?

6,000 bucks sounds like a lot... But only if you're just two people. As soon as kids and a house come into play, where constant things are "needed" for many years after moving in. Then it's quite little, especially since part of the income also disappears and/or, depending on the federal state, horrendous childcare fees are added.

Depending on the profession and prospects, you can be more or less relaxed about it – 6,000 bucks, as you call it, doesn't have to be the limit for young people.

Childcare in NRW when you have to work full-time was almost 800€ for under 2 years. From over 2 years it becomes significantly cheaper, but still over 400€. The fees depend on income. That really hurts. Now both children go to school and the afternoon care costs us 190€ plus 90€ for food for both children. So be careful, it can really get nasty expensive. Otherwise, you have at least 9 months to save a little financially for parental leave. With a 3k salary, there is at least 1800€ parental allowance. If you then stay at home for only 10 months (we did that with 2 children and managed it great), the tight belt stays manageable.

Childcare in NRW when you have to work full-time was almost €800 for under 2 years. From over 2 years it gets significantly cheaper, but still over €400. The fees depend on income. That really hurts. Now both children go to school and the afternoon care costs us €190 plus €90 for food for both children. So be careful, that can really get nasty expensive.

However, that depends heavily on the place of residence (respective regulations) and income.
Currently, for us under 3 years (there are no further distinctions) it would be "only" €553 for 45 hours in the highest income bracket.
A buddy from work pays nothing at all for under 3, because in his municipality ALL places are free. Crazy...