The typical asking rate per listing is in the $40's per square foot per year. The Alexandria submarket is going through a a rise in rates. In the last 3 months, the median rate went up $7 per sqft per year. That's a 18% rise in rent.
Compared to the rest of the Washington D.C. market, the Alexandria submarket has greater rates, and you'll need to make a great offer to be in this hot region.
In the last 90 days, 153 listings have been listed, so you'll want to check back regularly for new listings. About 1% of the office spaces in the Alexandria are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
Even though the median size is 3,282 sqft, there are still 0 spaces below 2,000 sqft. Most properties in this area are around 5 floors. Most buildings in this area were built in 1984 and are Class B.