Do you know what part of Alexandria interests you? There is Alexandria City, inside the beltway, and there is the Greater Mount Vernon area, along GW Parkway and Route 1, and there is the Fraconia/Kingstowne area. Many different zip codes, lifestyles, and home types.
If you're looking at condos, you can get a FREE guide to Alexandria condos at http://www.GuideToAlexandriaCondos.com.
This is such an open ended question. What size house are you interested in, garage, age, number bedrooms and baths. And what part of Alexandria? There is Alexandria City in the heart of Old Town, Landmark, areas near Annandale, Ft Belvoir, Kingstowne. Sounds like you need a Realtor to help you find the answers you want. Visit http://www.2hdb.com/kathystark to see all the homes on the market in Alexandria and other parts of Virginia or contact a Realtor who is an expert in the area you are interested in.
you can start here on trulia. Go to the "Real Estate Guides" tab up top and type in Alexandria, VA. The info is great! And I'm sure a local REALTOR will answer your shortly. Best of luck and happy hunting!