On average, listings lease in the $30's per square foot per year. The Fairfax submarket is going through a decrease in rates. In the last 3 months, the median rate decreased $1 per sqft per year. That's a 2% decrease in rent.
Compared to the rest of the Washington D.C. market, the Fairfax submarket has higher rates, and you'll need to make a great offer to be in this hot region.
In the last 90 days, 25 listings have been posted online, which means leases most likley are 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 2,340 sqft. Most buildings in this area are close to 5 stories. Most buildings in this area were built in 1985 and are Class B.