I am selling my entire house, since i am going away for Pesach.
Can someone use one of the bedrooms for sleeping only?
This can be done, but you must specify in the sale, that this room and any other which will be used is not included in the sale. These rooms need to be cleaned for Pesach, and a bedikas chametz needs to be performed.
If there are closets in the room you do not want to clean, they may be included in the sale, and closed and marked as sold to the non Jew.