The typical asking rate per listing is in the $30's per square foot per year. The Fairfax submarket is seeing a an increase in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 3% increase in rent.
Compared to the rest of the Washington D.C. market, the Fairfax region has less expensive rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 16 listings have been listed, which means spaces most likley are leasing quickly. 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 1,300 sqft. Most properties in this region are around 5 stories. Most buildings in this region were built in 1985 and are Class B.