If my mother/sister/daughter was a wet nurse, I’d have zero problems with it if they did it by their own choice. Same as if they were able to bottle and sell their own breastmilk for a couple extra bucks, kinda like how people are able to donate blood or plasma or semen for a little money sometimes.

Provided it’s not being abused and they are not enslaved or abused into doing it, I don’t see a problem with it

Edit: also that the milk went through a proper pasteurization process to ensure safety to anyone who was buying it