The typical asking rate per listing is in the $30's per square foot per year. The Pomona submarket is going through a a rise in rates. In the last 3 months, the median rate rose $1 per sqft per year. That's a 3% 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 region.
In the last 90 days, 43 listings have been posted online, so you'll want to check back regularly for new listings. 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 1,600 sqft. Most buildings in this region are close to 2 stories. Most buildings in this market were built in 1985 and are Class B.