If charging him rent, will turn the whole family relationship sour, I reckon you should not charge him. As said, you do not need extra money. In your situation, more like you guys need more communication. Cos sometimes to you it may be uncessary money, but to him he may have a different view. Talk to him, ask him why he does not like your cooking? Or maybe in future, when you cook, you do not need to cook his share. Tell him what you think and both of you guys try to accomodate one another. Your main intention is for him to live on his own(being independent). In another 2 more years, when he gets married, he will have to be independent and the guy that take cares of his family and finances. Real life situations will take a toll on him. You may even long that he comes home to visit you guys.