Dr. Monzer Kahf, a prominent economist and counsellor, states the following: According to Shari`ah, the property of each person in the family is separate and independent of each other, this also includes minors, not only children of the age 18 and above (Major). 

Regarding the earnings, the earning of a child, male or female, and major or minor, living with the parent or not belongs only to the child and the child alone has the right to do what she/he pleases with it. Of course, the guardians of the minors take decisions on behalf of minors and if the guardian abuses the properties of minor he/she is held responsible and can be charged for it even if he is the father. Mother and father are the alike in all the above.

A few more points remain to be added:

If parents or any one of them are in need, children are required to spend on them at the level they live as God instructed in the Qur’an 65:8. This obligation is not on the males only but it is on any of their children who is capable in terms of wealth and income including daughters and sons alike provided that if the girl is married. This rule applies to one who is rich herself not to the one whose husband is rich.

Kindness to parents may take the form of generosity and gifts, especially if a parent likes money. Go ahead and make him happy, you loose nothing that is worth his anger.

A working child who lives with his father, if the father asks, is required to reasonably share in the expenses of the family. The point here is that while a father is required to spend on his wife even if she is rich, he is not required to spend on his children if they are rich. Although it is rare (and to a large extent un-parental) that an able father would require his adult children to share expenses instead of saving and giving Sadaqat, he is not legally (in Shari’ah) responsible to spend on them unless they are in need.

Finally it is always not advised that children, adult or minors, and females or males should not take parts in their parents’ fights.”