I'm thinking of selling my sister's new clothes to the pawn shop.
Why do you want to sell your sister's stuff?
It's kind of a charity, I'm going to sell her stuff there for a higher price.
It would not be a good idea to sell your sister's clothes. They don't belong to you and you could get in trouble. You should sell your own things.
Whatever man. I'll do what I like to do.
First of all it's not charity to sell your clothes and second thing you don't have any rights to sell your sister's clothes without her permission. You should ask her first then sell them or else sell your own things if you're in desperate need of money.