Land purchase and house construction too risky in the current situation?

With children, many things just become more complicated. It's not simply "get up, have a quick breakfast, and go," but it drags on. Even everyday life without a construction site now requires so much more planning and time. The trip to the daycare before work takes time that you’re missing in the evenings. All this without even considering the construction site. Small children need constant care, except when they’re sleeping. If both parents want to work, care has to be secured, and not just from 9 a.m. to 1 p.m. Children usually go to bed a bit earlier too, so if you want to see the child in the evening, there isn’t much energy left for personal projects after work. Even just checking on the construction site is more complicated because small children have a talent for finding leftover nails, etc., and putting them in their mouth. The inspection with the electrician was also somewhat exhausting because someone at 14 months old already wanted to climb the ladder to the upper floor (and would have made it up there!). If I could choose, I would definitely tackle the house construction before having a child.

well, how long does it take?

A friend of mine also built with space for three children – then none came.

The risk exists, but it can also be that after the first one, none more come.

But then, in addition to job and small children, there is also house construction. That could be more complicated to manage. So maybe better to do job and house first, and when the little nest is finished and both are professionally established, then have the children. :) When the little children are there, starting to look for land and building/buying a house... brings some unrest into family life. The land is now being offered.

Then you have a nice hobby room for yourself.
I would calculate carefully... and with the equity, it will work well (if you reconsider must-haves like 80 sqm of storage space, i.e. a basement ;)).
Then you can do a lot yourselves and as a couple go into parental leave. Dads can help if they want to...

Do you really consider the statement "If the costs around the house continue to rise like this, perhaps a compensation levy or enormous property tax will be introduced, energy prices continue to explode, ..." to be so completely absurd? At present, it can be observed that the construction of single-family houses is politically and climatically the most unwelcome form of housing. I do not consider it impossible that legislation could change a lot for single-family homeowners in a negative way. Let's see how the property tax reform will develop. Allegedly, there are also supposed to be "winners", I am curious.

Then you have a nice hobby room for yourself. I would calculate carefully, .. and with the equity this will work well (if you reconsider must-haves of 80sqm storage space, i.e. cellar ;)). Then you can pitch in a lot and go to EL as a couple. Dads can help if they want. Recently it was said that the priority of the garden for children decreases rapidly once they start school or rather can hang out with like-minded peers on the playground nearby. Therefore, it does make sense to be finished by then.