Most municipalities have limits set on how many animals can reside in a home within city limits. For pet sitters who offer in home boarding, it can be an issue, especially if they have their own animals and already meet the limits.
In dicussion with animal control in 2 cities, the advice given was that they would only investigate an issue if a complaint is made by neighbours regarding number of animals, noise level or hygiene. Upon investigation, if they determine that an animal is/was present only for a short stay, and the number of animals actually registered that address is within limits, no further investigation would be required, and no action taken.
If there are any concerns whatsoever, contact your local animal control, or contact ACPSN to do it for you.