Acquire land, demolish the house and rebuild

With the tools, I'm lucky that I have several self-employed craftsmen in my circle of friends who would help out.

I just wanted to point out that it takes more than a few hands and a bucket of paint. When I think about how often I was at the hardware store.
Here, a paint roller, a few more brushes, and right away a 3-pack of tape for masking (I don’t know how many packs of tape I’ve bought like that), then an extra extension cord because the electrical wiring still hasn’t been switched from the construction power box, and so on.
None of these individually are large sums. But if you are at the hardware store almost every day, it adds up.

We had the garden (property in total 525m²), driveway, terrace and rainwater connection done up to the grass seeding, but without plants. Altogether that came to just over 20,000€. I don’t think quite half of that was labor; the rest was materials.
Even if you want to do it yourself gradually, you still need the money for the materials and maybe even a digger.

I think you want to save in the wrong place: 170sqm, divided over a 1(,5)-story building with a basement means: 100 sqm basement. In total, 270sqm of living and usable space. I don’t even want to know what this size is needed for. For 40,000 you get a cheap utility basement, but who needs 100sqm of usable and storage space? Then with an equipment plan that looks more like it was built before the millennium. This significantly limits the future value of the house. Quantity is simply not quality ;) Then I doubt that your self-employed friends can provide their equipment for a medium-term period, let alone help, because every day must bring in money for them. With the demolition, I see no problems with the current knowledge – this is a common process. I would reconsider the house project a bit and not approach the technology so naively. Regards Yvonne