On average, listings lease in the $20's per square foot per year. The Brea submarket is seeing a a boost in rates. In the last 3 months, the median rate went up $1 per sqft per year. That's a 3% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Brea region has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 17 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 6% of the available space in the Brea are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 6,070 sqft, there are still 0 office spaces below 2,000 sqft. Most properties in this area are close to 2 floors. Most buildings in this area were built in 1985 and are Class B.