Is it permissible to work in the maintenance of facilities belonging to usurious banks and other companies, and is the salary earned from this work unlawful, and is it permissible to perform Hajj with money saved from it?

It is not permissible to work in device maintenance in places designated for prohibited activities, such as usurious banks, because that constitutes aiding in sin. As for places designated for permissible activities, there is no objection to that. The salary for maintaining devices in usurious banks is not lawful. As for the validity of Hajj performed with ill-gotten wealth, there is a difference of opinion among jurists, but the majority hold that it is valid, though sinful. It is obligatory to restrict one's work to places designated for permissible matters, and it is advisable to perform Hajj with pure, lawful money.