Building a house now or in 3 years / interest rate development

Regarding the interest rate development ...

I also want the bank that makes such concrete statements and already knows now what will happen in a few years. With that, you could certainly make a lot of money if you play it right...

I am the sole earner since my girlfriend is still studying and would only be able to contribute financially after her studies (teaching degree)

When would she be finished?

But since we are planning to have a child in 3-5 years, her salary would probably be used primarily for savings and such expenses

A child means initially less income and higher expenses. Parental allowance is also limited. Usually, after the child is born, one cannot work 100% for a longer period.

I earn €2,250 net and also have a mini job on a €450 basis. So we could initially repay about €1,300 per month.

So, usually house construction in the classic case means that besides your job, you are heavily involved with the construction, the surroundings, or providing own labor.

How many working hours per week do you have in your main job + mini job?

The other thing is that €1,300 is only the rate to the bank. Additional costs still come on top. And then we are at €1,600. And usually, there are one or two surprises during construction or things you have to pay for that are not covered by the financing.

Even with the mini job, the house consumes you.

The bank has more or less already promised us the money.

Honestly? But the household calculation hasn’t been done in writing yet, right?

Sounds to me like an untrustworthy bank or an advisor looking for a quick deal. This is also indicated by the bank's statements "Zinsen werden auf jeden Fall steigen". These are just means to create subtle pressure on you to act. Stay away!

Buying a house is more than two sizes too big for you in your current situation.

Presumably, you can secure the property if plots are scarce in your area. But at that price, it rather doesn't sound like it? Could you roughly pay off the property within five years?

Otherwise, it simply won't work with the income, I agree with the previous posters.
What are you saving at the moment? Are you supporting your girlfriend now?

While reading along, I had the impression that there is roughly a limit at which the first forum members consider the project feasible, and that is about €100k loan amount for €1000 income (roughly!). You are miles away from that.

I have €300k "on my back" with €3800 net income and find that at the limit of what I can handle.

Reading the thread only now.

Which insane bank offers you such financing? You don’t know how you will build or what it will cost. Nevertheless, you want to take out a large loan, about which neither you nor the bank knows how it will realistically be repaid based on today’s conditions. The interest rate is probably a good deal for the bank.

Not the rising interest rates (they will rise, but whether I pay 1.5% or 2% doesn’t really matter – there won’t be an interest explosion unless another crisis occurs) are your problem, but the rising prices.

More or less promised does not mean that you already have the contract in your pocket. If the decision maker or the Black Box got involved, a refusal should actually come. Sorry.

The bank has more or less already promised us the money.

More or less? Only for the property?
You shouldn't know the other costs yet, right?