how would you handle this

My best friend got caught up with a narcissistic young lady and now they have a child. They break up and she's making his life a living hell. She keep asking for money when he already gave her, she's just draining him financially and using the child as a bait. Now she wanted to send his child to him so he can babysit the baby. She gave him rules when it comes to the child. She told him to don't have his girlfriend /whores around their child and he disagreed so she changed her mind because she don't want his girlfriend /whores help raise their child. So now he have to look for more money for a babysitter because of what she don't like. He asked for me advice but I'm not, sure what to tell him, but in all honesty he need to put his foot down and stop leaving her do what she wants.