What is the ruling on working for real estate financing companies in Saudi Arabia? Are the transactions they undertake, such as buying a property then selling it in installments at an increased price, tainted by usury? And is it permissible to work for them according to Sharia?

Real estate financing has multiple forms, and their rulings differ. The form mentioned in the question, which is Murabaha for the one who commands the purchase, is permissible in Islamic law. What indicates the permissibility of working in the aforementioned company is that it has a Shariah board, so one may work there in compliance with this board.