If I were the parent, I wont take house rent from my son or daughter, I will see it as my responsibility to shoulder but sill it will depend on my financial muscles at the time. If I'm strong and well to do, I won't put it on my ward to share the house rent with me instead I will encourage my ward to invest the money he's making into something profitable for himself and the family .
So you will be working on a 2-3 jobs to be able to pay rent/bills/buy food and clothes, while seeing your kid lays on a sofa and spending his money on, I dont know, branded clothes and gadgets? I fully agree that we are responsible for out children, and we should not ask for a financial help. But as I see it, we should raise or children so, that they understand that sometimes it is tough for a parents to do everything himself, and sometimes parents require help. Otherwise it looks like a voluntary slavery.