I read that you can perform Hajj in behalf of someone only if he/she is old or suffering from a sickness from which there is no hope of recovery.
My question is: How old does that person have to be? If he/she is over 50, does that count as old age? Would that mean I can perform hajj in behalf of that person? What is the minimum age someone has to be, such that he can send someone else to perform hajj for him?