Compared to the rest of the Metropolitan Los Angeles market, the Montclair region has more expensive rates, and you'll have to negotiate above asking rent to be in this hot submarket.
In the last 90 days, 3 listings have been posted online, which means new listings most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. 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 130 sqft. Most buildings in this area were built in 1979 and are Class B.