What is the ruling on working for a research company that conducts studies for both interest-based (usurious) and Islamic banks, knowing that the nature of the work involves personal interviews with clients about their opinions on the bank and its services, and that the questioner is in financial need and does not personally benefit from these studies?

It is permissible to work for a research company, provided that the research is not in a field that serves companies engaged in haram (definition) activities, such as usurious banks. This is because it falls under aiding in sin, which Allah has forbidden in His saying: "And do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty." Therefore, it is not permissible to fulfill any request to prepare research that serves an entity involved in forbidden activities.