How many square meters are realistic given the following financial situation?

Due to the Riester pension, I would calculate it carefully before canceling. After all, there are subsidies and tax benefits.

Riester pensions are generally not canceled; otherwise, you have to pay back all the subsidies (allowances and tax advantages) at once. After deducting the costs, you usually end up with a significant loss - mainly with insurance contracts.

If you are only concerned about the ongoing contributions, you can simply set the contract to contribution-free. Then the balance remains, but you do not pay new contributions. Usually, a short letter to your Riester provider requesting contribution suspension is sufficient. By the way: under certain conditions, you can also use the Riester balance in the future to repay the mortgage loan without having the allowances or tax benefits withdrawn again.

Have the calculated equity variants worked out for you. The rental income is gross. For the apartment, you need reserves - a basic capital stock. Consider which costs are planned (owner's meeting, administration, fees, taxes, reserve formation...) This is not a 1:1 calculation. What happens in case of tenant default? The risk is naturally greater with one apartment than with several. Rent increases, if applicable, should be secured through a graduated rental agreement.

You can also use the Riester balance under certain conditions in the future to repay the mortgage loan, without losing the allowances or tax benefits.

I used my Riester contract in this way and withdrew the chapter for the house construction. I can only advise against it. Bureaucracy without end, you "have to" live in the house for life (at least until retirement) (owner-occupied, otherwise allowances must be repaid!), and on my housing promotion account there is more than 1.5 times what I actually received. It now earns 3% interest and must be taxed upon retirement.

Hello dear ones,

thank you for your comments.

If you are only concerned about the ongoing contributions, you can simply suspend the contract without contributions. Then the credit remains, but you do not pay any new contributions.

That's probably what we will do.

We had our appointment with our architect over the weekend.
We did not explicitly tell her to go for 140 sqm, but rather gave her our budget framework: 400,000 EUR - 450,000 EUR. With the proceeds from the apartment and the increase through our own equity, we would then end up with external financing of 300,000 EUR - 350,000 EUR. As recommended here, thanks again for that.

Our architect then suggested whether we might want to go up to 500,000 EUR, since one could (even with little experience) save 50,000 - 60,000 EUR through own labor.
We initially agreed to this.

Now we have slept on it for two nights and are completely unsure whether that is actually realistic?! Can you on average save those 50,000 - 60,000 EUR?
Of course, we are also fortunate to get most of the building materials at employee prices.

Or should I quickly grab the phone and tell her the limit of 450,000 EUR after all?

In two to three weeks, we will hopefully receive our final floor plan :)

Have a nice start to the new week.

50,000 - 60,000 euros of personal contribution is a tough nut to crack. That is not done in a few weekends. I consider that quite optimistic.

In two to three weeks, we will hopefully receive our final floor plan :)

And what was actually "ordered?" The 500k€ version?