Heart and soul of this judgment from Hon’ble Apex Court is in Para 8.

In an illustrative case where wife was surviving by begging, would not amount to her ability to maintain herself. It can also be not said that the wife has been capable of earning but she was not making an effort to earn. Whether the deserted wife was unable to maintain herself, has to be decided on the basis of the material placed on record. Where the personal income of the wife is insufficient she can claim maintenance under Section 125 Cr.P.C. The test is whether the wife is in a position to maintain herself in the way she was used to in the place of her husband. In Bhagwan v. Kamla Devi (AIR 1975 SC 83) it was observed that the wife should be in a position to maintain standard of living which is neither luxurious nor penurious but what is consistent with status of a family. The expression “unable to maintain herself” does not mean that the wife must be absolutely destitute before she can apply for maintenance under Section 125 Cr.P.C.