Parents should not make a profit from their DC
However, many low income parents, unlike the better off mc, can't afford to keep another adult - or several - once they no longer receive benefits for them and once they affect the Council Tax
In such cases, DC who are earning should pay in full the extra they cost:
so calculate together their share of utilities, groceries, petrol, council tax etc
and the DC pay their own phones, tablets, clothes, going out etc
but not mortgage or rent, because the DC don't increase those costs