Most listings are in the $30's per square foot per year. The Brea region is going through a decline in rates. In the last 3 months, the median rate decreased $2 per sqft per year. That's a 5% decrease in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Brea submarket has smaller rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 15 listings have been posted online, which means office spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 13% of the office spaces in the Brea are subleases, so you might be able to find a shorter term or below market rent. 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 26,010 sqft, there are still 0 spaces below 2,000 sqft. Most properties in this market are approximately 2 floors. Most buildings in this region were built in 1985 and are Class B.