There is no one definitive answer to this question as the cost of becoming a Catholic can vary depending on a number of factors. However, some of the potential costs that may be incurred in the process of becoming a Catholic include attending Catholic schools or religious education classes, purchasing Catholic books and materials, making donations to the church, and participating in special events or retreats. In addition, those who are interested in becoming a Catholic may also need to undergo a period of instruction and study before being formally received into the church.