There are different orders of life in the Vedic system; some are single monks, and some are householders (family men). Each division and subdivision has a particular role to play especially for the generally spiritual upliftment of the society, and the life of a family man is no different. It is not that only the monks spread spiritual knowledge, as will be explained in the following purport by Srila Prabhupada.
To award fearlessness to the common man is the greatest act of charity. A sannyasi, or one who is in the renounced order of life, should wander from door to door, from village to village, from town to town and from country to country, all over the world as far as he is able to travel, and enlighten the householders about Krsna consciousness. A person who is a householder but is initiated by a sannyasi has the duty to spread Krsna consciousness at home; as far as possible, he should call his friends and neighbors to his house and hold classes in Krsna consciousness. Holding a class means chanting the holy name of Krsna and speaking from Bhagavad-gita or Srimad-Bhagavatam. There are immense literatures for spreading Krsna consciousness, and it is the duty of each and every householder to learn about Krsna from his sannyasi spiritual master. There is a division of labor in the Lord's service. The householder's duty is to earn money because a sannyasi is not supposed to earn money but is completely dependent on the householder. The householder should earn money by business or by profession and spend at least fifty percent of his income to spread Krsna consciousness; twenty-five percent he can spend for his family, and twenty-five percent he should save to meet emergencies. This example was shown by Rupa Gosvami, so devotees should follow it.