Water damage or stains are usually a sign of a roof problem. Interior General Sense of smell can tell you a lot when you first walk into a house. Musty smell could mean hidden water damage. Some animal damage can be very costly to remove. Check the windows and doors.
Floors Check the general condition of the floors.
Ceilings and walls Ceilings and walls usually show a lot. Cracks in walls can be very minor or very major. Water stains could mean a problem with the roof. Check the plumbing fixtures for cracks and general condition. Check as many electrical fixtures as possible.