a free loader
A freeloader is a person who gets everything for free and thinks they're doing you a favor, but they’re just being a total self-centered jerk.
He said he was helping the homeless, but he was just helping himself and his bank account.
She said she was helping me, but all she was doing was taking my money and my patience.
He told me he was helping the world, but he was just helping himself and his ego.