Buying a condominium together to rent it out

That is really a crazy idea! Either buy a smaller apartment alone or invest the money in the stock market.

If it is worth it, then many more would do it. There are quite a lot of private individuals who have multiple times the equity and are smart enough not to invest in residential investment properties... Investing in "Betongold" was a thing once, and later on, it went south for some.

Unfortunately, the market value does not increase so significantly that it exceeds taxes and interest, so that a profit occurs. And then the property is 10 years older and may still need renovation...

As a second point, I see that each of you is going into debt... What if one of you starts a family and cannot get a mortgage for a own home because "there" is already something going on?

First of all, you are always liable to each other to some extent. Just think about what happens if your buddy doesn’t pay his installment?!

If you both take out loans, you can immediately argue about whose bank/loan is ranked higher in the land register; with one loan you are fully liable. If the bank auctions the apartment, the other one has a problem.

Nevertheless, the question to the group: How does it work tax-wise, is the rent paid into a joint account and then halved and credited to the two owners on the tax return? I am currently considering the same. The background is that my brother and I want to buy an accessible condominium nearby together to secure our parents’ retirement. It is supposed to be rented out for the next few years until our parents (currently 60 years old) move in. The apartment would be financed without a loan; monetary profits are not the focus.

Nevertheless, the question to the group: How does it work from a tax perspective, is the rent paid into a joint account and then halved for the 2 owners when filing the tax return?

Do you want to hijack a crazy idea thread with a serious question?
On one hand, you would probably "classically" choose a GbR. But on the other hand, your motive might also be a crazy idea:

The background is that my brother and I want to buy a barrier-free condominium nearby together to secure our parents’ retirement.

Let’s think one step further: the parents become in need of care, the landlords are at the same time the ones who will be asked first by the social welfare office about their ability to contribute. Just ask a tax advisor if you’re not shooting yourself in the foot there.

Apart from that, even for the constellation

This is to be rented out for the next few years until our parents (currently 60 years old) move in there.

with only one apartment, the following applies,

Renting out with profit intention only works with risk diversification.

This applies accordingly if instead of the intention of profit a "mere" wish to not generate losses takes its place. To play with the same hobby fees as a single-property landlord, you might as well buy a houseboat. That way, the parents will get more out of the active retiree phase.