The typical asking rate per listing is in the $30's per square foot per year. The Brea region is experiencing a a rise in rates. In the last 3 months, the median rate rose $4 per sqft per year. That's a 14% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Brea region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 14 listings have been made available, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 7% of the available leases 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 posted, so finding a space for a small business might be tough.
Even though the median size is 3,590 sqft, there are still 0 new listings below 2,000 sqft. Most properties in this market are around 2 floors. Most buildings in this area were built in 1985 and are Class B.