The ancient wisdom of Babylon included a principle that is uncomfortable to think about when you are young: prepare for the time when you can no longer work as you do today. Age comes for everyone. Energy changes. Circumstances shift. The person who has built streams of future income before they need them is in a completely different position from the one who has not. A successful person in their thirties who has built no passive income or savings is one health event or economic shock away from difficulty. A person who has been building future income for ten years has options. The best time to build future income is when you least feel you need it — which is precisely when you have the energy and time to do it.