Most listings are in the $10's per square foot per year. The Alexandria submarket is going through a a boost in rates. In the last 3 months, the median rate rose $16 per sqft per year. That's a Inf% increase in rent.
In the last 90 days, 10 listings have come on the market, which means listings most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. 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 2,330 sqft. Most buildings in this market are approximately 2 floors. Most buildings in this region were built in 2004 and are Class C.