Mornington Peninsula Shire Council has kindly offered the following comments (in blue) relating to garage sales.
 
(If there is no blue answer on a particular question, then a comment wasn't made.)
 

• Are permits required? No permit required
• Are there any laws controlling the posting of garage sale signs? Garage sale signs may only be erected within the property boundary. No part of it may protrude past the property boundary line. They may not be affixed to any public land including power poles and other street signs.  The signs are especially dangerous at intersections and are not permitted on any part of the road, road reserve or intersection. If the resident wishes to place additional garage sale signage they may be erected within nearby prominent properties BUT ONLY with the property owners permission. All garage sale signs must be removed at the end of the day.
• Are there limits to how many garage sales one person can hold per year? You can have a garage sale as many times a year as you like.
• Are there laws about using the footpath in front of the person's house? Must be within property boundary line.
• Other comments offered.
• Is there a page on the web site that covers the laws relating to garage sales?

Disclaimer:
1) Laws are always subject to change.
2) If there is any doubt, you need to confirm current council laws.
3) egaragesales.com.au provides this information in good faith, but will not be held liable or responsible for any losses or penalties incurred as a result of changes to, or misinterpretation of, current council laws as amended from time to time.