Sometimes conditioned souls exchange money, but in due course of time, enmity arises because of cheating. Although there may be a tiny profit, the conditioned souls cease to be friends and become enemies.
As stated in Śrīmad-Bhāgavatam (5.5.8):
tayor mitho hṛdaya-granthim āhuḥ
janasya moho ’yam ahaṁ mameti
The monkeylike conditioned soul first becomes attached to sex, and when intercourse actually takes place he becomes more attached. He then requires some material comforts — apartment, house, food, friends, wealth and so on. In order to acquire these things he has to cheat others, and this creates enmity even among the most intimate friends. Sometimes this enmity is created between the conditioned soul and the father or spiritual master. Unless one is firmly fixed in the regulative principles, one may perform mischievous acts, even if one is a member of the Kṛṣṇa consciousness movement. We therefore advise our disciples to strictly follow the regulative principles; otherwise the most important movement for the upliftment of humanity will be hampered due to dissension among its members. Those who are serious about pushing forward this Kṛṣṇa consciousness movement should remember this and strictly follow the regulative principles so that their minds will not be disturbed.