The most important things financially are cash flow and coffer size. Being able to take on debt at advantageous times provides both of these things because it

The most important things financially are cash flow and coffer size. Being able to take on debt at advantageous times provides both of these things because it allows you to shift cash flow temporally and increase the money you have on hand at will. A rich person can translate portions of their future earnings into large amounts of capital on command, and this can come in the form of future anticipated earnings too (e.g., future anticipated rents or sales) while still being able to live on a day-to-day basis. Being able to control your current and future finances can also provide tax benefits if structured correctly. Poor people can't do that - they need all of their cash now just to live, all the time.