Is financing for house purchase / house construction feasible?

believing is not knowing.

can you say something?

@nordanney can you say something?

Normally the direction does not matter. The right is priced into the condition.

Regardless of whether we want to buy an object or build it ourselves, we estimate our financing framework at 300,000. The goal is to have a monthly rate of about 1000-1100 (excluding additional costs).

Why only a financing framework of 300,000 euros? Is that what the financial advisors said?

I'm not a fan of the "wait a little longer and save" faction. Anyone who followed this advice in the Düsseldorf area would have had to save a lot already to somewhat compensate for the price increase.
In NRW, you can look at the price increases of the standard land values through historical values of the last 10 years on Boris. Maybe you have this as well. Add another 5% increase in construction costs and you can roughly estimate how the price increase per year COULD be. No one has a crystal ball.

I know, that wasn't asked for, but anyway:

Well, at 27 with a 22-year-old girlfriend, I would never have thought about building a house. I would have rather invested more time in life and career. You also hear of many breakups that were driven, not least, by building a house.

In the end, everyone has to know that for themselves. Personally, I went wild at the end of my 20s, traveled with girlfriends, did a lot of mountain bike trips with buddies, etc. But here in the forum, that makes you more of an exotic. A lot of people have been pursuing the dream of owning a house since they were 12 and have always transferred 50% of their pocket money to the house account. I regret nothing. But in the end, it's always a matter of personality.

I agree with fab101, especially regarding the girlfriend at 22 years old. When I think about what I experienced and, above all, how much I personally developed between the ages of 22 and 30, I wouldn’t even bet on my relationship at that age. Plus, without having experienced the first 1-2 years of the child together, I wouldn’t dare to build on it. I can check that off. But I'm a professional pessimist.

But exactly such discussions don’t help the OP move forward. They have made their decision and need professional support. Period. Everyone is different and that’s a good thing!