On average, listings lease in the $20's per square foot per year. The Westlake Village region is going through a decline in rates. In the last 3 months, the median rate decreased $12 per sqft per year. That's a 30% decline in rent.
Compared to the rest of the Metropolitan Los Angeles market, the Westlake Village submarket has less expensive rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 18 listings have been posted online, which means listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 6% of the available leases in the Westlake Village are subleases, so you will probably need to consider the implications of signing a direct lease with the building. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,500 sqft. Most buildings in this area are close to 2 stories. Most buildings in this area were built in 1988 and are Class A.