My friend, monks and nuns in Christianity predate the origin of the Roman Catholic Church by almost 800 years. Christian monasticism first had its beginnings in the Egyptian deserts when certain believers found that they as individuals needed to live apart from society to keep themselves from becoming the man Jesus warned about in the parable of the sower: “...still others, like seed sown among thorns, hear the word; but the worries of this life, the deceitfulness of wealth and the desires for other things come in and choke the word, making it unfruitful.” (Mark 4:18-19). It isn’t a life for everyone, but we all can learn lessons from their experiences.
As far as pre-requisites go, that would depend on the specific order.