Most listings are in the $20's per square foot per year. The Brea region is going through a a rise in rates. In the last 3 months, the median rate went up $2 per sqft per year. That's a 6% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Brea region has lower rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 11 listings have been posted online, which means office spaces might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 9% of the office spaces in the Brea are subleases, so you will probably have to consider a longer term lease. 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 7,560 sqft, there are still 0 spaces below 2,000 sqft. Most buildings in this area are approximately 2 floors. Most buildings in this area were built in 1985 and are Class B.