The reason to use a dynamic code rather than printing a web address is what happens after the sign goes up. Listings move, prices drop, properties go under contract, and the sign is still in the yard. With a dynamic code you update the destination in seconds: from the listing to a sold announcement to a page of similar homes, without touching the sign.
A code on the rider also gives a curious passerby a way to act on the spot. Point it at a page with a booking form or your contact details, and a scan can become a showing request before the buyer leaves the street. On the Pro and Business plans, scan analytics shows each code's scans by day and hour, so with one code per sign you can see which streets and placements draw interest.
Riders are the natural place for the code: they are cheap to print and easy to move between signs. Print the rider with a generic call to action such as "Scan for photos and price," and when the listing closes, repoint the code and hang the same rider on your next property.