On average, listings lease in the $10's per square foot per year. The Brentwood region is seeing a an increase in rates. In the last 3 months, the median rate rose $3 per sqft per year. That's a 15% rise in rent.
In the last 90 days, 10 listings have been listed, which means office spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 60% of the listings in the Brentwood 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 on the market, so finding a space for a small business might be tough.
Even though the median size is 4,200 sqft, there are still 0 new availabilities below 2,000 sqft. Most buildings in this area are approximately 3 stories. Most buildings in this market were built in 1963 and are Class B.