>To offset this people can be paid to bring up a child that their parents cannot afford, this works great as the people who raise the other parents children are less likely to have children themselves.

You didn't think that through. They are less likely to have children because they have decided against children. A female lawyer isn't going to give up her career to take care of other people's children. She has much better options.

What may happen is that poor people get their children taken away and sent to another poor family that now gets paid for taking care of the child. It's basically a very "unorthodox" form of childcare/adoption without class mobility.