On average, listings lease in the $20's per square foot per year. The Fullerton submarket is going through a an increase in rates. In the last 3 months, the median rate increased $27 per sqft per year.
Compared to the rest of the Metropolitan Los Angeles market, the Fullerton region has lower 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 new listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 321% of the office spaces in the Fullerton are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,480 sqft. Most buildings in this area are close to 2 stories. Most buildings in this market were built in 1973 and are Class B.