Compared to the rest of the Metropolitan Los Angeles market, the Mission Viejo region has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 20 listings have come on the market, which means office spaces are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 15% of the available space in the Mission Viejo are subleases, so you might be able to find a shorter term or below market rent. 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 1,420 sqft. Most properties in this area are approximately 2 stories. Most buildings in this region were built in 1985 and are Class A.