What's the best option throw the kitchen sink at it every month?
Just start tbh. When I paid off all my cc debt during the pandemic (before then taking on more again

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I used the snowball method. Got it from a Dave Ramsey book and it worked well.
For your boy, first thing I’d say he should do is to make a budget/track where all his money is going then save up $1K ASAP and just put it out of mind. He’s staying rent free so it hopefully shouldn’t be too hard. The $1K is so if he has an emergency, he doesn't have to use CCs and go further into debt.
From there, have him write down his debt smallest to highest in terms of amount owed. So it might be:
CC1 - $500
CC2 - $2,000
Car Note - $5,000 etc
From there, just have him pay the minimum of every card, then whatever else he has extra, just throw it at the debt with the lowest owed until completed. Rinse and repeat until he’s done.
Some might say attack the debt with the highest interest rate and that’s fine, I just like the snowball method because you get a bit of a rush when you see a debt line item gone. Gives you the motivation to keep going.
Biggest thing for him will be to trim the expenses. Any money that would have gone to rent should go to knocking out debt. Cut back on frivolous spending and use extra money and attack the debt. Idk how much he has, but if he grits his teeth and pushes, he can make significant strides by end of year.