Most listings are in the $30's per square foot per year. The Stevenson Ranch submarket is going through a a boost in rates. In the last 3 months, the median rate went up $0 per sqft per year. That's a 0% increase in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Stevenson Ranch submarket has more expensive rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 4 listings have been listed, which means leases most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 25% of the listings in the Stevenson Ranch are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 2,300 sqft. Most buildings in this region are around 4 floors. Most buildings in this area were built in 2003 and are Class A.