On average, listings lease in the $20's per square foot per year. The Fairfax County region is experiencing a a rise in rates. In the last 3 months, the median rate went up $3 per sqft per year. That's a 13% increase in rent.
In the last 90 days, 13 listings have come on the market, which means new availabilities 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,220 sqft. Most properties in this area are close to 5 stories. Most buildings in this area were built in 1985 and are Class B.