What happens if you don't get a permit?
If a permit, when needed, is not obtained before construction, you have violated city codes and regulations; you'll be subject to fines and penalties. You'll be required to obtain permits for the work and it must pass inspection, or you'll have to return the structure or site to its original condition.
Remember... construction codes were created for safety reasons. Work built without a permit can be unsafe, no matter how good it looks.