What is a bedroom? For septic system purposes, the design has allows for 150 gallons per day of effluent per bedroom. However, the structure may not have that many bedrooms in fact. One might also rely upon the town's tax card as another source, but who knows what an assessor used. Regardless of the waste disposal system for the home, I feel that the most reliable definition is a room with a door, a closet (or place to easily provide one) and a separate means of egress (e.g. a window that someone could escape through in the event of a fire). The fire department has a precise definition of this size, but I would simply point out that a basement type window probably does not qualify unless it is a sufficently large double hung window. Vacation cottages and camps may have somewhat sketchier definitions and I have seen sleeping closets that I would not call a bedroom. As far as the MLS is concerned, you will find a range of interpretations as to how properties are listed.