Why add a room to your home if you've already got an empty basement downstairs? Basements can easily be transformed into recreation rooms, bar rooms, media rooms or "man caves," not to mention extra bedrooms or rental units, if there's a separate entrance -- and they bring in more money when you eventually sell. But don't just rush downstairs and start hammering away. It's important to make sure your lower-level remodel includes a bathroom, as the presence of a bathroom can dramatically increase its value. Also, try to avoid adding a lot of walls or hallways, which will make the area feel smaller and darker -- basements already tend to feel that way. Installing a gas fireplace is another way to make the area feel brighter and cozier. And don't forget to add storage space. You can never have too much of that!