According to Bhakti-rasāmṛta-sindhu, the science of devotional service, one should not eat more than what he requires to maintain body and soul together. Vegetable diets and milk are sufficient for maintenance of the human body, and therefore one has no need to eat anything more to satisfy the palate. One should also not accumulate money to become puffed up in the material world. One should earn his livelihood easily and honestly, for it is better to become a coolie for an honest livelihood than to become a great man in society by hook and crook. There is no harm if one becomes the richest man in the world by honest dealings, but one should not sacrifice the honest means of livelihood simply to accumulate wealth. Such an endeavor is harmful to devotional service. One should not talk nonsense. A devotee's business is to earn the favor of the Lord. Therefore a devotee should always glorify the Lord in His wonderful creations. A devotee should not decry the creation of the Lord, defying Him by saying that He has created a false world. The world is not false.
(Srimad Bhagavatam----2:8:21----purport).

It is advised that an advanced devotee should be tolerant; he should show complete mercy to persons who are ignorant or innocent. A preacher-devotee is meant to show mercy to innocent persons, whom he can elevate to devotional service. Everyone, by constitutional position, is an eternal servant of God. Therefore, a devotee's business is to awaken everyone's Kṛṣṇa consciousness. That is his mercy. As for a devotee's treatment of other devotees who are his equals, he should maintain friendship with them. His general view should be to see every living entity as part of the Supreme Lord. Different living entities appear in different forms of dress, but according to the instruction of the Bhagavad-gītā, a learned person sees all living entities equally. Such treatment by the devotee is very much appreciated by the Supreme Lord. It is said, therefore, that a saintly person is always tolerant and merciful, he is a friend to everyone, never an enemy to anyone, and he is peaceful. These are some of the good qualities of a devotee.
(Srimad Bhagavatam----4:11:13----purport).

A devotee should always aspire to live in the association of advanced devotees and engage in the service of the Lord through the paramparā system. One should serve the mission of Śrī Caitanya Mahāprabhu through the instructions of the great Gosvāmīs of Vṛndāvana. This is called tāṅdera caraṇa sevi. While serving the lotus feet of the Gosvāmīs, one should live in the association of devotees (bhakta-sane vāsa). This is the business of a devotee. A devotee should not aspire for material profit or lament for material loss. When Aṅgirā Ṛṣi and Nārada saw that Mahārāja Citraketu, an advanced devotee, had fallen in the darkness of ignorance and was lamenting for the material body of his son, by their causeless mercy they came to advise him so that he could be saved from this ignorance.
(Srimad Bhagavatam----6:15:18-19----purport).

A devotee's business is to offer obeisances to the Lord and the spiritual master constantly. This principle is the recognized way to come to the platform of bhakti. As soon as one comes to this platform, he gradually understands the Supreme Personality of Godhead, and simply by understanding Kṛṣṇa one is liberated from material bondage.
(Srimad Bhagavatam----8:1:15----purport).

According to the instructions of Śrīla Rūpa Gosvāmī, the first business of a devotee is to accept a bona fide spiritual master who can train him to engage his various senses in rendering transcendental service to the Lord.
(Srimad Bhagavatam----9:4:18-20----purport).

A devotee should be always alert whether he is wasting time or utilizing time. That is devotee's business.
( Lecture on Srimad Bhagavatam---2:1:3).

Devotee's business is to glorify. He doesn't take any credit for himself. Actually, there is nothing to be taken credit. The all credit goes to Kṛṣṇa.
( Lecture on Srimad Bhagavatam----3:26:42).

Caitanya Mahāprabhu was enquired by a devotee that "What is the business of a devotee? How he will make progress without any difficulty?" So Caitanya Mahāprabhu said in two lines that "A Vaiṣṇava should always avoid asat, materialistic person, always avoid the association.'.
( Lecture on Srimad Bhagavatam----6:1:25).

Therefore devotee's business is to know that everything belongs to Kṛṣṇa; it must be used for Kṛṣṇa. This is Kṛṣṇa consciousness.
( Lecture on Srimad Bhagavatam----6:1:31).

So a pure devotee's business is how to satisfy Kṛṣṇa.
( Lecture on Srimad Bhagavatam----6:2:11).

The devotee's business is he's always thinking of how to do good to the people in general, how they will accept Kṛṣṇa consciousness.
( Lecture on Srimad Bhagavatam----6:3:27-28).