There are constant arguments about working from home
One issue in real estate law that has repeatedly occupied the courts in recent years is the right to terminate a lease in connection with home offices. Can a landlord terminate a lease if they intend to use the tenant's apartment for professional or business purposes?
In the case of a termination of tenancy due to personal use, the landlord must, according to § 573 of the German Civil Code (BGB), invoke a "legitimate interest". However, such an interest only exists if the landlord intends to live in the rented apartment themselves or plans only minor business use, for example, using a room as a study or home office, or as a living room practice or law firm.
However, if the landlord wishes to terminate the tenancy for purely business-related reasons, this is only possible if the continuation of the tenancy would cause the landlord a "significant disadvantage" (see Section 573 of the German Civil Code, Paragraph 2, Sentence 3). This would be the case, for example, if the landlord had to rent a space for their professional activities at a cost higher than their income from their (freelance) professional work.
The criterion of insufficient profitability would also apply if the landlord possessed additional premises but could only use them professionally after extensive renovations or a complete refurbishment. Another legitimate reason for termination would be if "the landlord would be prevented from making reasonable economic use of the property by the continuation of the tenancy and would thereby suffer significant disadvantages.".
However, if the landlord terminates the lease, for example, because he or his spouse needs the rented apartment to set up another workplace including an archive, this is not a sufficient justification (see BGH judgment of 29.03 2017, VIII ZR 45/16).
Sources: iww.de > Mietrecht kompakt, immowelt.de, haufe.de, gesetze-im-internet.de