Is building a house possible with our income?

With a plot of land costing 20k€, the incidental purchase costs (property transfer tax, land register entry) are quite manageable. There probably won’t be any realtor fees, right?
Are the 1200€ the parental allowance or your wife’s income when she goes back to work? (at the desired number of hours)? So you have about 1000€ left per month?
If you really want it, I would probably first buy and pay off the land, that should go quite quickly. And otherwise save more so that at least some equity is available.

There is no realtor, fortunately.

The 1200€ is my wife’s income. Roughly about 1000€ remains, but it always depends on things like insurance etc.

Since house prices keep rising, no matter how much I save... For example, last year we had an offer of about 195k€... now it’s about 210k€.
We currently pay about 440€ rent including utilities for about 60m² with 2 children... that will work for one more year, but then it will get tight.

Well, with 300k, if that is enough for you, you will still have to stretch yourselves. Is rent included in your expenses? That would disappear. How much is it including additional costs? A big vacation won't be included.

I mean without own contribution and extreme compromises, it won't work. I personally would want to spend a maximum of €1100 for the house with that income (repayment, interest, additional costs). That is about €200k. I would not touch your equity - with a house and 2 cars and 2 children, that is actually the minimum you should have in the account. €200k - €20k plot - €30k additional costs. (Garage is already a luxury that does not fit the budget) That leaves €150k for the house. That is hardly possible. How about an existing property?

I mean without own contribution and extreme compromises it won't work. Personally, with that income I would be willing to spend a maximum of €1100 for the house (repayment, interest, additional costs). That's about €200k. I wouldn't touch your equity – with a house and 2 cars and 2 children that is basically the minimum you should have in the account. €200k - €20k land - €30k additional costs. (Garage is already a luxury that does not fit into the budget) That leaves €150k for the house. That's hardly possible. How about an existing property?

We are looking at existing houses on the side... But the prices some want (at today's rates), you could almost rebuild from scratch again...

Example: house should cost €80,000, but renovation costs amounted to over €100,000.

And I won't be getting a higher salary at the moment...

Well, with €300k, if that's enough for you, you will still have to stretch yourselves. Is rent included in your expenses? That would drop away. How high is it including additional costs? No big vacations will be possible

Yes, rent is included in the expenses! We pay €305 cold + €125 gas/electricity.

We want a house with land so that the children can go outside sometimes and we can relax as well. In the long run, having to go to my parents' or in-laws every time isn’t so great either...

So, at the moment, worse than poor situation.

Example: The house was supposed to cost €80,000, but renovation costs amounted to over €100,000.

That would put you at €200k, €200k for a new house is hardly possible.

Example: The house was supposed to cost €80,000, but renovation costs amounted to over €100,000.

The difference to new construction is still quite noticeable. You can only tend towards new construction if it is really financially feasible... that would already be extremely tight for you.