Compared to the rest of the Metropolitan Los Angeles market, the Fullerton region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 14 listings have come on the market, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. About 7% of the available leases in the Fullerton are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,500 sqft. Most properties in this market are close to 2 floors. Most buildings in this area were built in 1974 and are Class B.