I made custom stamps, & got blank labels. Blank labels are for my stamps for my plastic half dozen cartons.I write on the carton that they haven't been washed and should be washed before use. wouldn't take much more to add they aren't produced in an inspected facility... but I know who I sell to mostly, so I don't put anything on the carton for them cause they know the deal.
You can get blank egg cartons at TSC, FFH etc. If you want to get fancy and spend the extra $on cartons and labels you certainly can, but for me the cost of selling eggs with recycled egg cartons from the store and the going rate for eggs barely cover the cost of feed.
I reuse cartons, especially the ones from the store too. I also order blank cartons from Amazon.
I have made a quite abit of money selling eggs, actually. Almost $200. I'm at a slow streak with no one buying eggs at the moment, but it takes patience.