What is the ruling on working as a maintenance technician for a company affiliated with a usurious bank, knowing that the work site is in a commercial complex belonging to the bank, the salary is paid by the bank, and the work may sometimes require working inside the bank itself?

As long as the company's activity is permissible and has no relation to the usurious activity of the bank it belongs to, working for it is not deemed unlawful, though refraining from it is better. Its ruling is similar to working for an owner whose wealth is mixed (with unlawful earnings). However, maintaining the bank itself is impermissible.