The typical asking rate per listing is in the $30's per square foot per year. The Falls Church County region is going through a a boost in rates. In the last 3 months, the median rate rose $35 per sqft per year.
In the last 90 days, 5 listings have been listed, which means office spaces most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 540 sqft. Most buildings in this market are around 1 stories. Most buildings in this area were built in 1980 and are Class B.