Most listings are in the $10's per square foot per year. The Orange County region is going through a a rise in rates. In the last 3 months, the median rate increased $17 per sqft per year.
In the last 90 days, 32 listings have been listed, which means listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 31% of the office spaces in the Orange County are subleases, so you might be able to snag a great spot on a short term. 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 2,350 sqft. Most properties in this area are approximately 2 stories. Most buildings in this region were built in 1985 and are Class A.