Most listings are in the $30's per square foot per year. The Fairfax County region is experiencing a a boost in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 3% increase in rent.
In the last 90 days, 16 listings have been made available, which means new availabilities are probably leasing quickly. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,300 sqft. Most properties in this market are approximately 5 stories. Most buildings in this region were built in 1985 and are Class B.