Some of the expenses you will need to consider while living in İstanbul include:
Housing: some leasing contracts may include security deposit which is often two months’ worth of rent. Keep this in mind as part of your housing expenses.
Transportation: you may choose to opt for a monthly pass if you plan to use public transport regularly on your daily commute. Check for student/teacher discounts.
Mobile phone sim cards: Vodafone, Turkcell and Turk Telekom are the major GSM providers in Türkiye. They offer different packages. You can buy a sim card at the airport or you can visit one of the GSM stores around the city. Check their webpages for up-to-date information about their prices and offers.