To compare cost of living in various towns go here: http://www.bestplaces.net/col/
Lately I've shown many condos, townhomes and development homes in Bridgewater, Somerville, Bernardsville, Chattham, Summit and have to tell you the complexes and towns can vary greatly, you'll need to take a road trip tour to ultimately find what is best for you.
Beaver Brook and Alton Place in Clinton, Chambers Brooks in Branchburg, Bridgewater Oaks, Bridle Club are all developments offering basements and some space. They are generally below $400,000 so hopefully they fit your price range. Feel free to contact me further about any of these towns and what they have to offer.