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

My girlfriend and I are planning to build a house.
We found a plot nearby, for which we have initially reserved. The plot would cost us about €65,000.

We have no equity because we used it last year for a car purchase. Notary, land registry, etc. we could cover ourselves, but not much more.

The plot has a building obligation of 5 years. This means we now face the choice of whether to start building next year or only in 3 years.

I am the sole earner because my girlfriend is still studying and could only contribute financially after her studies (teaching degree). But since we plan to have a child in 3-5 years, her salary would probably be used primarily for savings and similar expenses anyway. The bank also suggested that we have the option to make special payments.

So we are now faced with the choice: do we take out €65,000 and build in 3 years and then take out another loan? Or do we take out everything now (about €400,000) and start building in spring 2020?
The bank has more or less already assured us the money. I earn €2,250 net and have a side job on a €450 basis. So we could initially pay about €1,300 per month.

The bank said that interest rates would rise enormously, as would construction costs. Therefore, (according to the bank) building next year would be cheaper than in three years.

What do you think? Can you give us some advice on this?
I also wonder if it makes sense to take out part of the money now for the plot and then another part for the house construction in 3 years?

May I ask how old your girlfriend is and how much longer she is expected to study? And where could her workplace be later on, or where is she most likely to work?

Die Bank meinte, dass die Zinsen enorm ansteigen würden,

Oh really? Is the property fully developed or do contributions still have to be paid?

So I have to be honest, I’m getting a bit uneasy about the numbers (and I’m not one of those who immediately shout stop if there is little or no equity or something like that). Are you sure that a 400k loan is enough if already 65k (how much real estate transfer tax will be added?) goes towards the property? The income is not particularly high in relation to the loan amount, and if a child is still supposed to come, there won’t be much more overall income even after the studies. How long will she be studying? Is it already certain that she will actually get a job in your area? (Fixed-term/permanent?) Where are you building or where would the property be?

What you are planning is a big financial adventure and very risky. You have no equity, low net income, and want to build a house in more expensive times?

Your bank can no more see the future than I can. My prediction: interest rates will stay the same, but building will become slightly more expensive

Under the current conditions, such a project is absolutely irresponsible. Repayment + incidental costs would already be about €1,700 alone. In addition, there is a desire to have children shortly after graduation. You would be living at the absolute limit for the next 5-8 years.

So we are now faced with the choice: do we take out €65,000 and build in 3 years and then take out another loan again? Or do we take out everything now (about €400,000) and start building the house in spring 2020.
The bank has more or less already guaranteed us the money. I earn €2,250 net and also have a side job on a €450 basis. So we could initially pay about €1,300 per month.

The bank said that interest rates would rise enormously, as would construction costs. Therefore (according to the bank), building next year would be cheaper than waiting three years.

Both are bold statements from the bank.

65k with that salary yes, 400k with €2,250 net definitely no. Too risky, even if you are young.

No one can say anything about interest rate developments and construction costs. These are purely speculative.

Basically, you are both young and unmarried. I don’t want to paint a black picture, but a lot can happen in 3 years.