Most listings are in the $20's per square foot per year. The Whittier region is going through a a boost in rates. In the last 3 months, the median rate went up $8 per sqft per year. That's a 40% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Whittier region has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 53 listings have come on the market, so you'll want to check back regularly for new listings. About 4% of the listings in the Whittier are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 1,510 sqft. Most properties in this region are around 2 stories. Most buildings in this area were built in 1974 and are Class C.