First of all, thanks again for any input. I gratefully take all of that into my considerations.
Over the past two days, I took the trouble to create an overview of all expenses within a year. Not only for planning the financing, but because I always wanted to see where money quietly goes in everyday life. We were quite surprised by some items – e.g., Lieferando, expenses for gifts, etc. We also became aware again of how carefree we live (or can live), which in itself is a great privilege. We also found some saving potentials along the way, but that should remain irrelevant and unconsidered in this calculation for now. :)
In addition, to work with a buffer right away, I based the expenses on the last 13.5 months as "annual expenses" and rounded up almost all positions – which makes quite a difference with hundreds of individual items. Furthermore, I treated myself to an absolute luxury item last year for about €6,500, which is also included – in other words, nothing was sugar-coated, but rather calculated to our disadvantage. :)
After that, I compared the annual income (current and 2024) with the annual expenses and calculated the monthly "surplus" from that. Then I added the currently saved cold rent and subtracted mobility costs of €400. According to my calculation, that would be the absolute maximum possible rate.
Of course, one should deduct some amount from this despite the aforementioned buffer to avoid being overwhelmed by the smallest issue.
The conclusion: Even if we didn’t live one bit differently than we do now, we could already afford a maximum rate of €2,200. In 2024, even €2,500.
Since we have now also found saving potentials that we are partly tackling immediately, the calculation for 2024 without really painful restrictions and only temporary renunciation of the above-mentioned unnecessary luxury items would even allow a maximum rate of €3,200.
So, I see that in 2024 we can afford between €2,300 and €3,200. Simply because we are very cautious people, I would go with the lowest value. Nevertheless, I feel pretty confirmed with the €2,500, and honestly, that gives me a very good feeling. Before an actual financing, I would update the numbers again to be absolutely sure.
On the subject of mobility:
We could take over a car from the family. That means mobility costs do not have to include purchase costs, leasing rates, or anything like that, only tax, fuel, insurance. We would not need a second car, as there are enough unused cars in the immediate family that could be used in an "emergency," and my fiancée intends to take a remote job.
On the subject of rising living standards:
We find most things that others with high incomes strive for quite boring. We don’t need an expensive car; the Opel we can take over from the family is enough for us. We don’t need a vacation in Bali or 3 weeks in the USA. Of course, we’ll probably do that someday – but if the house is paid off first, the first few years will be spent at home or maybe a week at the Baltic Sea, no problem. We don’t buy expensive clothes, expensive jewelry, or any other classic "luxury." At most, we have a weakness for our hobbies – espresso machines, bicycles, home cinema, and similar. On the one hand, we are now so well equipped there that no big purchases will have to be made in the next few years; on the other hand, we are always very careful only to spend money that is actually there. If the hobbies have to take place with the equipment we have for the next 10 years, then so be it. There is simply no other way.
To say it plainly: We are absolutely resistant to letting our living standards slip. We have exactly one "luxury" dream: A great house with a great garden where you can live as a family. That’s it. I come from a working-class family where every purchase was and still is carefully weighed. If I waste money senselessly, I get reprimanded. o_O:D