It makes a big (financial) difference whether 1 or 2 children are planned, accordingly a second income is sometimes missing for quite a long time. My wife went back to full-time work 16 months after the birth of our second child. But that only works because my parents live next door, our older child is in kindergarten, and I have extremely flexible working hours and a suitable job. I don’t know any other couple among our acquaintances where both work full-time with two toddlers. It’s not exactly ideal. We are now also considering reducing working hours again.
Building costs of just under 700k including a granny flat and incidental building costs is ambitious (but not impossible) if everything is to be awarded? Nothing has been said about that yet. Is there already a contract with a general contractor or individual trades?
That is one of the points I worry about the most. You can plan a lot, but how things really turn out with children in reality, you can of course never predict or want to live in "constant stress" to pay off the house and reduce the time spent with the children. On the other hand, we both mainly work from home and our parents (on both sides) live in the neighboring village.
There is no contract yet, but we are close to awarding to individual trades. Own work is present to a certain extent, but we are not professionals and cannot take over entire areas. My husband has experience on construction sites and will mainly assist with the shell construction; otherwise, it will mostly come down to "preparatory work" to reduce craftsmen hours, and laying floors, milling grooves, etc. The own work is not yet included in the cost estimate.