Most listings are in the $20's per square foot per year. The Warrenton region is seeing a a boost in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 5% increase in rent.
Compared to the rest of the Washington D.C. market, the Warrenton submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 3 listings have been listed, which means new listings are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 600% of the listings in the Warrenton are subleases, so you might be able to snag a great spot on a short term. 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 1,110 sqft. Most properties in this market are close to 3 floors. Most buildings in this area were built in 1991 and are Class A.