Most listings are in the $20's per square foot per year. The Annandale region is experiencing a a rise in rates. In the last 3 months, the median rate went up $29 per sqft per year.
Compared to the rest of the Washington D.C. market, the Annandale region has lower rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 4 listings have come on the market, which means office spaces are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 475% of the listings in the Annandale are subleases, so you might be able to find a shorter term or below market rent. 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 1,200 sqft. Most buildings in this region are approximately 4 floors. Most buildings in this area were built in 1986 and are Class A.