Some clergy members make vows of poverty, thus choosing to live and die without any wealth. Their sponsoring institutions provide their housing, food, clothes, and other necessities, both during working years and after retirement.
Other clergy support themselves and need to earn incomes, save resources, and make provision for their elderly years.
If you’re really asking about deceitful televangelists, illegally and unethically enriching themselves through good-faith donations, that’s another matter with a clear answer.