Its complicated...
The simple answer is for women to hold off on having sex and children until a man proves with his actions that he is willing and, most importantly, able to protect and provide for her and any children they might have.
The problem is that women can and often do have sex with men out of their league. If women had to wait to have sex to weed out the men who just want a nut or men who have nothing going for them or no future ambitions, a lot of women would be disappointed at the actual level of men they attract for a long term commitment.
The reality is, a lot of women would rather be a booty call to a baller or have a handsome bum play househusband than to seek out the relationships on their level