Minecraft wiki entry for Building_a_metropolis, associated text: Small apartment: Approximately 45 square meters internal area. This apartment is likely to be cramped, but also cheap. 1-3 rooms, 0-1 bathrooms, 1 bedroom.
Medium apartment: Apartment with 1-2 bedrooms, 1-2 bathrooms, a kitchen, and at least one other room. Typically 80 to 150 square meter exterior.
Penthouse apartment: Singular or nearly singular nice apartment on the top floor of a high-rise building. Easily over 200 square meter exterior with at least 1 bedroom per couple/individual and many additional rooms of all sorts. Anyone who lives here is likely the equivalent of at least a millionaire.