You can sell them at any age as long as the buyer is capable of giving the bottles. It would be best if they were on milk that the new owner has access too, so either a replacer or cow's milk if they don't have goat milk. I have sold them as young as a week.
Webare picking up our first this weekend. She will be on two a day bottles when we bring her home. Many people in my area would sell as bb and pick Up was by day two....
I sold a two day triplet as a bottle baby this year. He was sold to another breeder who bottle feeds all their babies. I knew they could handle getting baby on a bottle (at two days it's pretty easy IMO) and they had plenty of goat milk for him and lots of other baby goats.
Normally, I'd keep until at least 2 weeks so they can be disbudded and have a day or two to recover and so they can go to 3/4 bottles a day since many people won't/can't do more than that. I still don't sell lots of bottle babies and don't sell them to "new" goat owners at that age unless they are close and want to stay in touch or have an experienced goat mentor to help them. Oh- and goat milk. There is just so much that can go wrong with babies.
We sell 80% of our babies weaned since we mostly dam raise. I don't have to milk at night for a while that way and it's been great for our milk production. I totally get, however, farms who sell at 2 weeks as bottle babies and just milk twice a day to have a simpler work load and get the babies out of there faster. Plus- people just love buying cute bottle babies so financially it probably makes the most sense.
Thanks for the info. As of now, my buyer has backed out. I had a local lady who wanted any doelings I might have for $150 each, pretty much as soon as they had colostrum. I have 3 high percentage Boer does and 1 mutt due to drop anytime. I am kind of glad she backed out. What's the point of having babies if you don't get to enjoy them. The goat market is pretty hot here, I'm not worried about finding buyers.