면 갚다

if X, pay it back

A conditional "-(으)면" plus 갚다, "repay". All five lines here are about money owed and the condition for returning it: take the medical costs out of it and pay it back when you have money, they joke that you have to pay it back once you get a job, borrow it and pay it back in two years, this way they do repay it. 갚다 is settling a debt or returning a favour, unlike 돌려주다, which is just giving a thing back.