There is no law saying at this point you have to do anything. But, it neither the buyer nor the seller has any representation who is going to arrange all the paperwork and make sure that all your rights and interests are protected? The seller traditionally pays both agents. The commissions come out of the sellers proceeds. Besides if you let your agent handle the negotiations you can most likely get the home for less with more concessions that you might not have thought of.
I personally recommend you let your broker handle the sale. He will only get half the commission but, they will end up doing twice the work since there is no one on the the other end to handle the sellers requirements.