When can a kitten leave its mom and start eating regular food?

You need to wait at least 6 weeks (every week is VERY important), and 8 weeks is best. Although you dont see it, the mother is socializing them, and taking the cat away too early will make things harder (so the cat can either turn out very timid or very aggressive, and it is very hard to change this). I know you’re excited and really want the kitten, but have a little patience. You dont give cats milk. That apparently gives some of them diarrhea. There’s special kitten milk you can find in the pet store. There’s also kitten food. It generally is best if the cat starts being weaned off mom’s milk slowly, but if you get the kitten and it hasnt been weaned, well you can just start it off on kitten food. Sometimes you can soak the dry food in warm water. Wet food is obviously good (canned stuff). Oh, and you might try this to reduce the crying when you bring the kitty home, since you are friends with the cat owner, see if you cant take over like a little stuffed toy you can rub over the kitten and the mum so their smells rub off, and then you can bring it home with the kitten. Might help with the transition.