The necessities of a sadhak should be as few as possible; for there are only a very few things that are real necessities in life. The rest are either utilities or things decorative to life or luxuries.
These a Yogi has a right to possess or enjoy only on one of two conditions —
(1) if he uses them during his sadhana solely to train himself in possessing things without attachment or desire and learn to use them rightly, in harmony with the Divine Will, with a proper handling, a just organisation, arrangement and measure
(2) if he has already attained a true freedom from desire and attachment and is not in the least moved or affected in any way by loss or withholding or deprival.
If he has any greed, desire, demand, claim for possession or enjoyment, any anxiety, grief, anger or vexation when denied or deprived, he is not free in spirit and his use of the things he possesses is contrary to the spirit of sadhana. Even if he is free in spirit, he will not be fit for possession if he has not learned to use things not for himself, but for the Divine Will, as an instrument, with the right knowledge and action in the use for the proper equipment of a life lived not for oneself but for and in the Divine.
Ref: Letters on Yoga – IV