Most listings are in the $20's per square foot per year. The San Dimas submarket is seeing a a boost in rates. In the last 3 months, the median rate increased $10 per sqft per year. That's a 52% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the San Dimas region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 25 listings have been made available, which means listings might be going fast. You'll want to be prepared to make an offer immediately. 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 1,730 sqft. Most properties in this region are around 2 floors. Most buildings in this market were built in 1989 and are Class B.