We are going to be staying at my in-laws house for Pesach, but they won’t be there. They will be selling their Chametz there. Can we do Bedikas Chametz there even if we are not the owner of the house? And, what are my obligations regarding cleaning the house for Pesach? We will be cleaning and Kashering a part of the kitchen, and otherwise, the house has been cleaned.
Someone who intends to travel on Erev Pesach in order to spend Pesach in a different location should not sell their entire property to a non-Jew as Chametz . Rather, at least one room must not be included in the sale in order to be able to perform Bedikas Chametz in at least part of his home.
A person who travels before the night of the fourteenth of Nissan need not leave a room unsold. Instead, they are obligated to perform Bedikas Chametz wherever they may be. A guest in another’s home should place some of their own Chametz in the room where they are staying and conduct a search for Chametz tonight. (Technically, a guest can fulfill their obligation to search for Chametz tonight via the search conducted by his host. In that case, the host acts as his guest’s Shliach for Bedikas Chametz).
A guest who owns no Chametz is not obligated to search at all. Someone who wishes to be Machmir, however, will make a point of bringing some Chametz of their own in order to conduct a search, but should nevertheless listen to, and rely upon, the host’s recital of the blessing over the search. If the host won’t be there, they can make their own Bracha.
(Some suggest that a guest should rent the room in which they are staying from their host (using a rent method that is Halachically valid e.g. paying money) in order to conduct the search.)
I am not understanding your last sentence. As a general rule whatever areas you will be using must be cleaned and Bedikas Chametz performed, and the rest (which the Chametz in those areas will be sold by the owner) must be marked off so one won’t by mistake go to those areas.
עיין סי’ תלז בתחלתו ובסי’ תנא בתחלתו.