Do you need a city permit to have a yardsale?
This varies from city to city, but most everywhere you can have a couple a year on your property. If you have them frequently (in PA that means more than 3 or 4 a year) you are SUPPOSED to get a state tax number and collect taxes on the items sold. Because at that frequency, the state considers you a business.
...not in the city that I live in.
as long as its on YOUR lawn. im sure its okay.