I am in Phoenix too.  We have discussed this at length in other threads so you might want to do a search.  Although it is technically on the books, the city does not seem to have the desire or the resources to enforce and constantly supervise it, and the last few city council meetings seem to be leaning toward letting the individual HOA's determine this.  If you are doing this on a large scale as a registered business with many properties then you may find it harder to fly under the radar however.  What is your HOA's policy on the matter?