Most listings are in the $30's per square foot per year. The Costa Mesa region is going through a a rise in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 4% rise in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Costa Mesa submarket has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 69 listings have been listed, so you'll want to check back regularly for new listings. About 3% of the office spaces in the Costa Mesa are subleases, so you will probably have to consider a longer term lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,330 sqft. Most buildings in this area are close to 2 stories. Most buildings in this region were built in 1983 and are Class A.