If one has a family member who hasn’t sold his chametz over Pesach (due to ignorance), can one go into that house on Pesach? Is there a fear that one may come to eat chametz like in certain cases of gentiles having chametz in front of Jews where we advise a mechitza to be in between or do we say that since they don’t really keep kosher that there is no fear? What happens if the relative than offers kosher for Passover cookies in a closed boxe etc?
It is permitted to visit the house as a guest, and the obligation of bedikah and bi’ur applies specifically to the owner of the house. Outside one’s own house, we also don’t find the concern that a person should come to eat the chametz. Yet, one should not live there on a “permanent” basis (Hilchos Chag Be-Chag p. 118), for fear of coming to eat the chamtetz.