enough so i could retire at the age of 18

Similar but I would want enough that I could have retired the moment I was born and enough so that my children and the children of my children could retire at that age as well.
Though I do not really find it appropriate to talk about children after a sex change >.> because quite frankly after something like that I highly doubt there would be any children from me ever again.
So there probably is not actually a amount of money that could ever make me do that.