My experiences with having roommates in the United States varied a lot. Sometimes the landlord just didn't care, or at most just asked to be informed. Sometimes they wanted to check the potential roommate's credit rating, or even go so far as adding them to the lease or rental contract.
Laws regarding renter's rights vary in different places in Germany, but in the city-state of Berlin, there are a number of peculiar aspects to what should be a fairly simple process: getting a roommate.
You are required by Berlin law to have the landlord's permission to sublet (untermieten) before your roommate, the subletter (der Untermieter, die Untermieterin), moves in.
Na ja, Sie sind doch der Vermieter hier.
Well, you're the landlord here.Play Caption
Bis sie eine Erlaubnis bekommen...
Until they receive permission...Play Caption
Hast du Mitbewohner? Ja, ich habe eine Mitbewohnerin. Ihr Name ist Sarah.
Do you have roommates? Yes, I have a roommate. Her name is Sarah.
Captions 5-6, Drei Leute: beim KofferpackenPlay Caption
The genders of the above are der Vermieter or die Vermieterin; der Mitbewohner or die Mitbewohnerin; die Erlaubnis.
If you don't ask the landlord's permission first, and either the landlord or somebody from the property management (die Hausverwaltung) notices a new name on the doorbell or mailbox, you could have a serious problem. If the landlord can prove you are subletting without permission—which is actually quite difficult without your roommate openly admitting it—you and your roommate could be evicted (zwangsgeräumt) from your apartment.
On a more positive note, however, if you have valid reasons, such as not wanting to live alone and/or wanting to save money on your costs of living, the landlord is required by law to grant you permission. First, you write them a letter asking permission to have a subletter and giving the personal details about your roommate such as their full name (der Vollname), date of birth (das Geburtsdatum), place of birth (der Geburtsort), and their last residential address (die letzte Wohnanschrift), and give valid reasons for wanting a roommate. The only legal reasons they might have for refusing are if your roommate has a bad rental history record or if there is less than 12.5 square meters (about 135 square feet) per person in the flat.
If the landlord fails to answer you within the period you asked them to, usually two weeks, you can get a lawyer to file against them and have the court order the landlord to give you permission. There are a number of renter's rights organizations in Berlin that, for a yearly fee of around 100 euros, offer free legal help, from advice all the way to the courtroom. It's smart to belong to one of these organizations!
Ich will Jura studieren und Rechtsanwältin werden.
I want to study law and become a lawyer.
Caption 42, Küss mich, Frosch: Für immer Frosch?Play Caption
Ihrer Klage sehen wir gelassen entgegen.
We are calmly looking forward to your lawsuit.
Caption 21, Marga Engel schlägt zurück: BetrugPlay Caption
The gender variants for "lawyer" are der Rechtsanwalt and die Rechtsanwältin.
Unless you are subletting your entire flat, the landlord is not allowed to stipulate any conditions in their permission to sublet, such as a limited time period or based upon a yearly verification of your income. Even if you agreed to such conditions originally, they can be invalidated in court because the landlord was not allowed to stipulate them in the first place.
Once you get permission for your roommate to live with you, you should have them sign a sublet contract (der Untermietvertrag) and then fill out—and this is a real mouthful–eine Wohnungsgeberbescheinigung, which can be translated as "a housing provider certificate." Your roommate needs one of these so that they can get a residential registration (die Meldebestätigung) at your address. Without a valid residential registration, they will have a lot problems with things such as getting a library card, a bank account, or a residence permit!
Thankfully, renters have a lot of rights in Berlin, but you may sometimes find yourself in the position of having to fight for those rights. Joining a renter's rights association is a good option and gives you full access to advice from experienced lawyers.
If you are in the mood to get into some advanced German, read this article about a decision of the Landgericht Berlin about subletting rights by the Berliner Mietergemeinschaft. You can also go to Yabla German and find other videos with some of the German vocabulary words mentioned above!