You are still wrong. The renter must obtain permission from the landlord prior to subletting and must substantiate legitimate interest. Not doing so is a breach

You are still wrong. The renter must obtain permission from the landlord prior to subletting and must substantiate legitimate interest. Not doing so is a breach of contract and can ultimately lead to termination of your rental contract. If the landlord does not grant permission your only option is to sue. While legitimate interest is interpreted broadly, it doesn‘t mean „anything goes“. „I want to earn money on a cheap rental contract that I can sublet for more money“ is not legitimate interest. The legitimate interest must also be rooted in something that occurred after you signed the rental contract. „I can‘t afford this flat, so I‘ll still sign the rental contract and then sublet“ will not create a legitimate interest that requires your landlord to grant the permission. „My income situation has deteriorated after signing the contract“ has better chances of passing the test. Some examples of what does and doesn‘t constitute legitimate interest here https://www.mietrecht.org/untervermietung/berechtigtes-interesse-untervermietung-gruende/ https://www.mietrecht.org/untervermietung/berechtigtes-inter... The landlord can also deny the request if they have an overriding interest, for example if they expect that the sublet would disturb the community in the building. Contrast that with where permission is not required, for example having a second job. The only requirement is that you must notify your employer. You don‘t need to substantiate anything. The only option for your employer is to deny this on very narrow grounds. If they don‘t respond to your notification within reasonable time, you‘re in the clear. This is fundamentally different from the required legal procedure when subletting.