The typical asking rate per listing is in the $30's per square foot per year. The Pomona submarket is going through a a boost in rates. In the last 3 months, the median rate rose $12 per sqft per year. That's a 62% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Pomona region has less expensive rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 16 listings have been posted online, which means listings are probably going fast. You'll want to be prepared to make an offer immediately. There aren't many listings below 2,000 square feet on the market, 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 around 2 stories. Most buildings in this area were built in 1983 and are Class B.