On average, listings lease in the $20's per square foot per year. The Leesburg region is going through a decline in rates. In the last 3 months, the median rate fell $7 per sqft per year. That's a 23% decline in rent.
Compared to the rest of the Washington D.C. market, the Leesburg region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 4 listings have come on the market, which means leases might be leasing quickly. You'll want to be prepared to make an offer immediately. About 100% of the listings in the Leesburg are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 900 sqft. Most properties in this market are approximately 3 stories. Most buildings in this market were built in 1990 and are Class B.