If he wishes to extend the term, he must provide her with another dowry (Sadaq), whether small or large, as mutually agreed upon. The dowry applies to both Mut'ah and permanent marriage. There is no inheritance between them in Mut'ah if one of them dies during the specified term. It is permissible for a man to contract Mut'ah even if he has a wife and is residing with her in the same city.
Commentary #2