Is real estate rental profitable?

Please note that when renting out a garage without an apartment, value-added tax (19%) must be paid.

Uh, no. As written, that is not correct. It’s like with the photovoltaic system. Analogous to the small business regulation. So normally, as a private person, you already need an entire garage facility or a small parking garage to reach the necessary turnover (20 garages at €75 per month, for example, is still little). But if you already have a photovoltaic system on the roof and have opted for VAT, you are already a commercial garage landlord.