It is very risky to accept money or food from materialistic persons, for such acceptance pollutes the mind of the charity’s recipient. According to the Vedic system, one should give charity to sannyāsīs and brāhmaṇas because one who thus gives charity becomes free from sinful activities. Formerly, therefore, brāhmaṇas would not accept charity from a person unless he were very pious. Lord Caitanya Mahāprabhu gave this instruction for all spiritual masters. Materialistic persons who are not inclined to give up their sinful activities like illicit sex, intoxication, gambling and meat-eating sometimes want to become our disciples, but, unlike professional spiritual masters who accept disciples regardless of their condition, Vaiṣṇavas do not accept such cheap disciples. One must at least agree to abide by the rules and regulations for a disciple before a Vaiṣṇava ācārya can accept him. In fact, a Vaiṣṇava should not even accept charity or food from persons who do not follow the rules and regulations of the Vaiṣṇava principles.
Ref >> Srila Prabhupada Vani.