The typical asking rate per listing is in the $20's per square foot per year. The Leesburg region is seeing a a rise in rates. In the last 3 months, the median rate increased $29 per sqft per year.
Compared to the rest of the Washington D.C. market, the Leesburg submarket 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 listed, which means spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 350% of the office spaces in the Leesburg 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 1,720 sqft. Most properties in this region are around 3 floors. Most buildings in this area were built in 1990 and are Class B.