Ron, one of our readers, posted this news at Counties with Few or No Codes.
Navaho county, Arizona has a new regulation that allows unpermitted structures that cost less than $500. The norm is 120 sq. ft. before needing a permit, which is rather limiting. Use local natural materials such as poles, earth, etc. to keep costs low and you can build larger.
People should read the county site and it is a bit different than this. The 500 dollar part is right.
Always read up on the county codes before buying land or building anything.