I don’t think that would ever function. Poor people ARE going to have children too, even if you could argue that they can’t provide well enough for the kids. Are there any countries in the world where poor people don’t have children? Personally - even though having children is no right - I much rather live in a society where it is possible to have children even if you have a very low income. Like you can in my country (Sweden). We still have a well functioning market economy.