On average, listings lease in the $30's per square foot per year. The Reston region is experiencing a a rise in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 4% increase in rent.
Compared to the rest of the Washington D.C. market, the Reston submarket has greater rates, and you'll need to make a great offer to be in this hot region.
In the last 90 days, 40 listings have been posted online, which means office spaces most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 5% of the listings in the Reston 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 4,790 sqft, there are still 0 listings below 2,000 sqft. Most properties in this market are close to 5 floors. Most buildings in this area were built in 1987 and are Class A.