New construction - now, in 3 years, or never?

These are three alternatives, of which I do not really see the middle one as given, and I would also phrase it differently: "Property bought with encumbered potential, return or possible development?" If you do not sell it immediately, I would at most wait for the upcoming government formation and then reconsider the assessment ("yes" or "no," I do not see "later").

Thank you very much for the answers. They have clarified my question. Immediate resale is currently not the best solution. Better to wait.

They have formulated my question more clearly. Immediate resale is currently not the best solution. Better to wait.

And then? Construction prices will rise, but...

Future salary growth is hard to say.

What will happen in the next two years that makes you hopeful?

That should settle the topic of house construction.

The issue of notary and property transfer tax should be regulated in the original purchase contract. Have a look. Normally, the municipality imposes the notary and property transfer tax on you (so, unlike the "normal" case, because the municipality has no interest in bearing the costs). If, contrary to expectations, nothing is stated in the original contract, then the municipality pays both the notary and the property transfer tax.
You can calculate a possible prepayment penalty online. It depends on your interest rate level compared to the bank's reinvestment options at the time of repayment (NOT to be confused with a current loan interest rate. Nobody cares about that, only reinvestment in specifically defined securities counts).
Without more detailed knowledge, your loss can therefore range from €0 up to a low five-figure amount. You are lucky that such a low property transfer tax is applied in Bavaria.

Neighbor’s house is already there, which is unfavorable. Ideally, it has a basement and you do not build one. In all other cases, you have higher costs to ensure the stability of the neighbor’s house.
An extension with the same profile is manageable, second best is stone on stone, best if it is a prefabricated house from the same provider, but always with an additional mortgage because the neighbor’s house is already standing.
I hope the plot doesn’t have further pitfalls. How flat is it, what does the soil quality say, show the neighbor’s ground floor plan within the plot with heights.
As a significant adjustment screw, I also see the width of your house. In the construction method, there is no potential anyway, wooden construction costs the same with identical fittings. If you build, then best with the same architect and at least the same shell construction company.

Neighbor’s house with basement was built by the neighbor and his relative with their own hands stone by stone, no shell construction company involved. Building without a basement is certainly cheaper for us. We will ask for the neighbor’s floor plan. Thanks again for the honest answer.

I wouldn't be discouraged so quickly. First, you might consider planning the house a bit smaller. 125 sqm is really sufficient for 4 people. It’s not royal, but very efficient and proven millions of times. If you calculate 3000/sqm construction costs, you could save at least about 30,000 euros.

Furthermore, banks roughly consider one third of the net income as an acceptable loan burden. But you can also go higher. This happens quickly especially with lower incomes. However, it is usually not a problem. People with lower incomes also live more efficiently and don’t have to give up much if the installment is higher.

I did the same myself and probably belong to the low earners here in the forum. At the bank, I first had to present my living costs and explain to them that I don’t do or have many expensive things. For me, these include, for example, a car and expensive trips. The bank employee actually asked me if I could stick to not taking expensive flights in the future.

That should settle the topic of house construction.

The topic of notary and real estate transfer tax should be regulated in the original purchase contract. Have a look. Normally, the municipality imposes the notary and the real estate transfer tax on you (so differently than it is "normal," since the municipality has no interest in bearing the costs). If, contrary to expectations, nothing is stated in the original contract, then the municipality pays both the notary and the real estate transfer tax.
You can calculate a possible prepayment penalty online. It depends on your interest rate level compared to the bank's reinvestment opportunities at the repayment date (NOT to be confused with today's loan interest rate. Nobody cares about that; only reinvestment in specifically defined securities counts).
Without further knowledge, your damage can therefore range from €0 up to a low five-digit amount. You are lucky that such a low real estate transfer tax is applied in Bavaria.

Thank you very much for the answers. I will read the purchase contract and find out the regulation.

What are you currently saving? Are large salary jumps through changing jobs realistic?

Thank you for your answer. Working part-time to full-time, you can earn more.