Ok...first out, figure out what the monthly income is after deductions. Net income. Following that, list every expense in a regular month
Credit Cards (if applies)
Note the difference from income in and expenditures out. Then divide it by 4.5 to see what kind of free cash is avaiable per week.
Open a direct withdrawal savings account, right from your sons bank (savings or chequing acct). I am not 100% sure of the savings options in the US, but that forced withdrawl every month, invested in some kind of GIC, or RSP, or education fund or even invested in the markets will turn results
Remember constant contribution is key to success.
Net Income minus- Expenses minus Forced Savings = Pocket Change for whatever...
Your son will be impressed at the monthly standings in his Forced Savings account and make it all worthwhile, next thing you know he will be buying real estate