Most listings are in the $30's per square foot per year. The Fairfax County region is going through a a boost in rates. In the last 3 months, the median rate rose $3 per sqft per year. That's a 10% increase in rent.
In the last 90 days, 234 listings have been made available, so you'll want to check back regularly for new listings. About 130% of the available leases in the Fairfax County 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 available, so finding a space for a small business might be tough.
Even though the median size is 5,000 sqft, there are still 0 new listings below 2,000 sqft. Most properties in this market are approximately 4 floors. Most buildings in this region were built in 1987 and are Class A.