On average, listings lease in the $20's per square foot per year. The Orange submarket is going through a a rise in rates. In the last 3 months, the median rate went up $2 per sqft per year. That's a 8% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Orange region has less expensive rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 64 listings have come on the market, so you'll want to check back regularly for new listings. 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 2,090 sqft. Most buildings in this market are approximately 2 stories. Most buildings in this market were built in 1980 and are Class B.