Why does Mark give Randy a check, what might they do with the money and how do they part?

Mark gives Randy a check to cash as reserve for his family and anything he needs. If nothing happens they agree to buy good liquor for a party. Mark confirms Randy will take care of Helen and be kind to her. He tells Randy how loyal and faithful they are to one another. Mark and Randy say goodbye and Mark boards. Randy drives away and stops unseen to hold back his tears.