I don't ship, only sell locally, and I don't sell to make money, so bear that in mind. But I've stopped selling anything younger than 3 months unless the buyer can prove to me that they know what they're doing.
My first year selling 2 week old babies, I got an angry phone call 2 weeks later from someone that had bought two that "got sick and died." And she wanted replacements for free. After asking about care (feed, temps, etc) I come to find out that despite my express instructions to the contrary, this lady has just stuck them out in a coop. She said "but it's temperature controlled!" but only to 70.... after that, no babies to anyone that doesn't come to me able to tell ME how to take care of them so I know it won't go in one ear and out the other

I also hand out a care sheet that includes my number and my vet's number. I give them a coccidia and a worming round before they leave if they're 3 months or older.
Now we have a grow out pen that's inside a barn completely, with a cement floor that we empty and sanitize twice a year, so we overwinter birds before selling, and I hand out a care sheet with written instructions and both my phone number and the phone number of my vet just in case. It costs more to keep them over winter, but I'm not raising them for money, so I'm fine with making sure they can are going to thrive wherever they go.