The typical asking rate per listing is in the $30's per square foot per year. The Brentwood region is going through a a rise in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 2% rise in rent.
In the last 90 days, 10 listings have been listed, which means new listings are probably going fast. You'll want to be prepared to make an offer immediately. About 20% of the available leases in the Brentwood 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.
Even though the median size is 5,100 sqft, there are still 0 leases below 2,000 sqft. Most properties in this market are close to 3 stories. Most buildings in this area were built in 1994 and are Class A.