No doubt it's not easy for him, but just putting a couple hours of effort for his sister - renting a flat for her and letting her stay there, for instance, - would've likely prevented her whole flight across the nation. As it is, it seems he just chucked her some money and left it at that.
naah.. up till today I can't bring myself to symphatize with Sayu's decision to leave the house and sell herself but looking at her mom, I kinda think that her decision is actually way better than staying at the house. Her mom is insane and super selfish.