On average, listings lease in the $20's per square foot per year. The Annandale region is going through a a rise in rates. In the last 3 months, the median rate rose $29 per sqft per year. That's a Inf% rise in rent.
Compared to the rest of the Washington D.C. market, the Annandale submarket has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 1 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 available, so finding a space for a small business might be tough.
Even though the median size is 2,560 sqft, there are still 0 leases below 2,000 sqft. Most properties in this market are around 10 floors. Most buildings in this area were built in 1986 and are Class A.