Is house construction financing possible? - Fully paid-off house

I would also tend to lean towards an extension or expansion. That makes the most financial sense. I could also imagine an expanded, insulated, and heated garden shed. However, it could fail if you work with classified information.

Total investment for a 130 sqm house without a basement, but including incidental construction costs, land, garage, and outdoor facilities?

I definitely do not consider 500,000 EUR as a total investment to be an exaggeration, even in a very rural area with low land prices. That can happen very quickly, especially if no personal contribution is planned.

we would then move to a somewhat more rural area. So do you think that even if we find a plot for 100,000 euros, the house would easily cost over 300,000 with a garage? So with a garage and outdoor facilities around 500,000? then we would rather discard the plan...

Financially, that would probably be doable. You have a lot of equity if you sell your current house. However, you should discuss beforehand what you really want. You could be completely debt-free in a few years and have a paid-off house in your mid-30s. That is absolute luxury and only very few can afford it!! If your work allows, you can reduce your hours and spend a lot of time with the children. Probably many dream of that who have just built a house in their mid-30s.

When I hear that, I’m really a little jealous
That’s not possible for us, but I am currently really enjoying working from home and thus being able to spend much more time with the children.

You can get a free estimate on the blue landlord platform. That’s how I always do it with existing properties when the street is known.

Another question. The house was purchased in 2014. Is it allowed to be sold again before 2024 without paying the exorbitant taxes?

Presumably not, but if construction of the new building were to begin in 3 years, that should be reasonably okay.