Deciphering advertisements
German accommodation advertisements do not refer to the number of bedrooms in flats and houses, but to square metres of floor space (das Quadratmeter; m²). Floor space is also the means by which most rents for rooms in "Wohngemeinschaften" are usually calculated. You might for example see a phrase such as "65m² Wohnfläche", which means "65 square metres of living space". This living space normally comprises living room, dining room and bedroom(s).
Adverts may also refer to the total number of rooms in a residence - excluding the bathroom, hall and kitchen. So if you want a flat with a living room, a dining room and two bedrooms, then look for adverts with (4 Zimmer), or as the abbreviation in advertisements would have it (4Zi).