The typical asking rate per listing is in the $10's per square foot per year. The Montclair region is experiencing a decrease in rates. In the last 3 months, the median rate fell $26 per sqft per year. That's a 57% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Montclair submarket has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 0 listings have been posted online, which means spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About NaN% of the listings in the Montclair are subleases, so you will probably have to consider a longer term lease. 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 1,030 sqft. Most buildings in this market were built in 1979 and are Class B.