The typical asking rate per listing is in the $10's per square foot per year. The La Center region is seeing a a rise in rates. In the last 3 months, the median rate increased $16 per sqft per year.
Compared to the rest of the Greater Portland market, the La Center region has smaller rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 2 listings have been made available, which means new availabilities most likley are going fast. You'll want to be prepared to make an offer immediately. 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 600 sqft. Most buildings in this area were built in 2003 and are Class B.