What is the legal ruling on taking a fee for cashing work checks for someone who does not have a bank account in America?

It is permissible to purchase an immediate, certified check or its equivalent with a currency different from its own, for more or less than its value, because the only condition is mutual possession (qabd), and the possession of a certified check is equivalent to the possession of its content. However, if the purchase is made with the same currency, an increase (riba - usury) is not permissible, but it is permissible to cash the check for its owner in exchange for a fee.