Many of your questions should focus on potential problems and maintenance issues. Does anything need to be replaced? What things require ongoing maintenance (e.g., paint, roof, HVAC, appliances, carpet)? Also ask about the house and neighborhood, focusing on quality of life issues. Be sure the seller's or real estate agent's answers are clear and complete. Ask questions until you understand all of the information they've given. Making a list of questions ahead of time will help you organize your thoughts and arrange all of the information you receive.
Have your duct system tested for air leaks. Many think that windows and doors are the major cause of a home’s air leaks. But according to recent research by the Department of Energy, gaps, cracks and disconnections in the typical home’s duct system are much more significant. The DOE states that the typical duct system loses 25 to 40 percent of the energy put out by the central furnace, heat or air conditioner. Leaks are usually the biggest problem.