OK so not so much about a kid walking over the parents...
My thought was that if you have the 18yr old living with you the child support assessment for the child stops. So 18yr old is no longer part of the equation, even though he is living with you and even if he is paying board, it is unlikely to cover the actual expenses of the kid... But then neither does child support....
So scenario 1
17yr old lives with you. 15 yr old lives with other parent. Both parents earn about the same. NO Child support either way. But 18 year old isn't assessed. So then the scenario is one parent has 100% care of 15yr old and hence gets the full child support, while the other parent is still dealing with 18yr old but with no financial support from the other parent.
My thought was that if you have the 18yr old living with you the child support assessment for the child stops. So 18yr old is no longer part of the equation, even though he is living with you and even if he is paying board, it is unlikely to cover the actual expenses of the kid... But then neither does child support....
So scenario 1
17yr old lives with you. 15 yr old lives with other parent. Both parents earn about the same. NO Child support either way. But 18 year old isn't assessed. So then the scenario is one parent has 100% care of 15yr old and hence gets the full child support, while the other parent is still dealing with 18yr old but with no financial support from the other parent.