Compared to the rest of the Washington D.C. market, the Annandale region has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 4 listings have been posted online, which means listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 500% of the available leases 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 available, 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 close to 4 floors. Most buildings in this market were built in 1986 and are Class A.