Most listings are in the $10's per square foot per year. The Orange County region is experiencing a an increase in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 7% increase in rent.
In the last 90 days, 23 listings have been made available, which means office spaces most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,000 sqft. Most buildings in this region are close to 2 stories. Most buildings in this area were built in 1987 and are Class A.