I don't know what to do

My boyfriend wants to go to Seattle. I don't want him to because he works a part time job and has other bills to pay for and he has a settlement with his car soon. I've tried to tell him that it's not a good idea cuz he's young with not a lot of money and he should do something smarter with all the money he'll be spending but he insists on going. What do I do to make him understand that it's a bad idea ?