I don't live in Mesa, Arizona, but I think the general rule applies all over the United States. Report to the Police about any annoying, hazardous, or unhealthy conditions that you have observed in your messy renter next door. They will send a code enforcement officer to check out your complaint. Your messy neighbor will be given a period of time to correct the situation. Failing that, your messy neighbor will be evicted. In extreme cases, your messy neighbor's rental property may be demolished if it is deemed unsafe for habitation.
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