On average, listings lease in the $30's per square foot per year. The Pomona region is seeing a an increase in rates. In the last 3 months, the median rate went up $9 per sqft per year. That's a 40% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Pomona submarket has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 15 listings have been made available, which means office spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 buildings in this market are around 2 floors. Most buildings in this area were built in 1983 and are Class B.