1. Women’s right to be sugar babies, instead of a wife, is limited. We don’t know if it’s legal or not. http://www.thefrisky.com/2009-04-13/whats-the-difference-between-having-a-sugar-daddy-prostitution/ Making the deal explicit is illegal. This severely limit women’s freedom.
2. Women do not have a right to set the amount of child support before conception. For example, say a billionaire is willing to impregnate her if the child support is less than $2k per month. Say she agrees. Well that agreement won’t hold out in court. The only way she can commit not to ask for more than $2k per month in child support is to actually pick a man that can only afford $2k per month.
3. Women’s right to share a man is heavily restricted. It’s grey area. Government may argue that it’s effectively polygamy or charge the women with prostitution.