If you're looking to build a 20x20 commercial building, the average cost is between $10 and $12 per square foot. This means your total cost would be between $200,000 and $240,000. Of course, this number can vary depending on the materials you use, the location of your property, the type of foundation you need, etc. But this gives you a general idea of what you can expect to pay for a project like this.