Mr Bennet received a letter from Mr Gardiner. In the letter it was mentioned that Wickham would agree to marrying Lydia if some financial conditions regarding Lydia were met. What were these financial conditions?

From the text:

All that is required of you is, to assure to your daughter, by settlement, her equal share of the five thousand pounds secured among your children after the decease of yourself and my sister; and, moreover, to enter into an engagement of allowing her, during your life, one hundred pounds per annum.