The special qualification of the pure devotee is that he is always thinking of Kṛṣṇa without considering the time or place. There should be no impediments. He should be able to carry out his service anywhere and at any time. Some say that the devotee should remain in holy places like Vṛndāvana or some holy town where the Lord lived, but a pure devotee can live anywhere and create the atmosphere of Vṛndāvana by his devotional service. It was Śrī Advaita who told Lord Caitanya, "Wherever You are, O Lord—there is Vṛndavana.
Bhagavad-gītā As It Is 8.14