The typical asking rate per listing is in the $30's per square foot per year. The Fairfax region is seeing a a rise in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 4% rise in rent.
Compared to the rest of the Washington D.C. market, the Fairfax submarket has lower rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 31 listings have been made available, which means office spaces are probably going fast. You'll want to be prepared to make an offer immediately. About 194% of the office spaces in the Fairfax are subleases, so you might be able to snag a great spot on a short term. 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 1,230 sqft. Most properties in this area are approximately 3 stories. Most buildings in this market were built in 1985 and are Class B.