I predict that he will do without the cough medicine rather than paying for it himself.
That stinks. Not only is he blond but he’s a miser, too!
That’s not helping things. Does he contribute to the groceries and other things involved in running a house?
My kids did a third...their share, when they had jobs, before they left home.
As you get ready to go get the koff medicine reach into the fredigitator and grab some of something he espeically likes. Then tell him that’s how you pay for his koff medicine.
Maybe if you grab all the rest of what he likes it will start to induce a change of behavior.