Is the waiting period (iddah) obligatory for a divorced Christian wife? Does the husband have the right to impose it on her? What is the ruling on the husband remaining in the wife's house after separation due to the unavailability of other housing?

Firstly: According to the Hanafis, Malikis, Shafi'is, and Hanbalis, a Kitābī (People of the Book) wife observes the waiting period ('iddah) for divorce and death just like a Muslim woman. This is based on the general textual evidences that mandate the 'iddah without differentiating between them if the husband is Muslim.

Secondly: Residing with a woman observing the 'iddah differs according to the type of divorce. If the divorce is revocable (raj'ī), there is no objection to living together because she is still considered a wife. However, if the divorce is irrevocable (bā'in), she is a stranger (ajnabiyyah), and it is not permissible to look at her or be in seclusion with her. It becomes difficult for them to remain in the same house while adhering to Islamic regulations, unless the house is large enough to allocate a separate section for him with its own facilities and private entrance. Otherwise, it is difficult to ensure safety from prohibitions.