Most listings are in the $20's per square foot per year. The Brentwood region is going through a a boost in rates. In the last 3 months, the median rate rose $29 per sqft per year.
In the last 90 days, 2 listings have come on the market, which means new availabilities 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,200 sqft. Most buildings in this area are approximately 4 floors. Most buildings in this region were built in 2001 and are Class A.