The typical asking rate per listing is in the $20's per square foot per year. The Fullerton submarket is going through a a boost in rates. In the last 3 months, the median rate rose $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 undervalued region.
In the last 90 days, 14 listings have come on the market, which means office spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 321% of the listings 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 available, 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 properties in this market are approximately 2 floors. Most buildings in this market were built in 1973 and are Class B.