Compared to the rest of the Metropolitan Los Angeles market, the Montclair submarket has higher rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 2 listings have come on the market, which means leases 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 130 sqft. Most buildings in this region were built in 1979 and are Class B.