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You made it more understanding to me now. A folk might have more income than the other while the other will have more discretionary income to invest with. So the income does not determine if the discretionary income will be high to invest with what determines our discretionary income is actually how less the bills and expenses at hand can be. For someone having more but taking much responsibility to himself he might have less discretionary income compared to a folk who earn less but have little expenses to make with no responsibility.
Well, there might be a way to manage our expenses even if there are some expenses that are mandatory every month. Like our utility bills, gas, feeding to mention a few others. Cutting down unnecessary expenses will increase our discretionary income.
Of course, some kinds of expenses are more discretionary than others, and surely it might be difficult to cut down on utility bills or rent, unless maybe we moved to another location, and some kinds of food is more economical than other kinds of food, but we have to be careful in terms of buying low quality food. Sometimes we can figure out ways to save money buy buying larger quantities of good food and then splitting up with neighbors who agree to share the costs.
Another thing is that some of our expenses, might cause social consequences for us, and so sometimes we are socially pressured to spend more, and probably we need to maintain some of those kinds of expenses in order to maintain good relations with others.
Regarding income, we might not always know how we might be able to earn more income, and there can be real trade offs in terms of how we want to spend our time, and so we might need to work more but we also might need to spend time organizing ourselves and our finances and we also might need to spend time with family, even if it is not resulting in higher income. Yet, sometimes if we have a job, we might identify some ways that we can work extra hours or that we might be able to work fewer hours and earn the same amount,.... including that we might see that if we spend 40 hours taking a certain kind of a course, we might be able to get a certain kind of extra work that relates to our having had gotten that extra certification, and so sometimes our time and our money might be better spent in order to improve our future income generating possibilities.