Hi gkl123,
I must say i am very shocked at the amount people are suggesting you charge your son!! I think there are somethings you need to consider :
Does he have a student loan that he is having to currently pay back?
Are you doing all his cooking, washing, buying his food and cleaning his room still?
Are you dependant on his rent money?
Does he have a car? Is he paying for it or are you? Insurance payments?
I feel that �350 is a little excessive and unfair, how is he ever going to save any money to move out if you charge that much? By the time travel expenses, clothing expenses for personal or work, mobile phone bills to pay out etc he will have tuppence left to spend to enjoy himself with!!! This could result in him borrowing money and getting himself into debt.
I'm not saying don't charge him anthing because i do think that its an importance lesson to learn!!
Hope this helps and good luck!!