On average, listings lease in the $10's per square foot per year. The Rexburg submarket is going through a a boost in rates. In the last 3 months, the median rate increased $15 per sqft per year.
In the last 90 days, 5 listings have been posted online, which means spaces are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 20% of the office spaces in the Rexburg 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 posted, so finding a space for a small business might be tough.
Even though the median size is 5,000 sqft, there are still 0 listings below 2,000 sqft. Most properties in this area are close to 2 stories. Most buildings in this market were built in 2006 and are Class A.