How much house can I get for my budget?

Budget increased to 300k, of which 50k is for the land, leaving 250k for the house.

Only want to have the shell including roof and windows done, will do the rest myself because there are enough skilled people in the family who can help me with plumbing and electrical!

Have a concrete offer for the shell as desired for 180k EUR binding!

Outdoor area initially left out, if there is still budget left then yes, otherwise not for the time being!

With 70000 minus the ancillary construction costs, you won't get far.

Skilled craftsmen in the area are nice and all, but you surely don’t get the materials for interior construction for free. That costs several thousand euros.

So, here in the Lower Bavaria region, we have providers that offer turnkey with basement under 200k (115 m²). Without a basement, 180k is also possible. It is a small regional company with a homepage where house types and prices are listed. The company has been on the market for over 20 years and has already built a few hundred houses. What turnkey means here, however, I cannot say.....but it should be somewhat more than "shell construction".

Of course, you can get a habitable house for under 200k. And you can also do the interior fittings of a house for 70k. But on the one hand, we are talking about 180k for the shell construction (so there is still a bit more to do than laying floors, painting, and attaching a faucet), and on the other hand, a house that costs 180k for the shell construction usually costs significantly more than 70k for completion. And anyone who thinks they can do interior finishing "just like that" by themselves and with friends should have no job on the side and a lot of (very good) friends who have no hobbies and live off an inheritance. The question is also whether you want a construction site as a garden for years.

250k for a house is certainly no problem, but not with the given approach.