This is all really a big straw-man. The OP did not ask, what is material happiness. Or is it relative. It basically asked is there an underlying behaviour or state of mind in the millionaire that can be grasped as a consistent life-philosophy which can be applied by anyone in their Goal to material success (regardless of what amount an individual conceives as successful.) Material happiness is not the same thing as spiritual happiness. Material gratification is not the same thing as spiritual gratification, and i am not interested in debated that distinction. You can make another thread if you want and i might pop by. I am talking about the philosophy of money making.
Books like “The habits of millionaires” and “The Secret” imply that there is a philsophy.
I spend whole yesterday reflecting on this issue and I know this discussion would emerge, so I avoided to post my conclusions in the end of the day. But let me risk some words. Now my points may contain many mistakes, because despite me being very passionate about philosophy I am ashamed I am yet to read one book.
First thing, maybe it was unintentional but the poster asked his question in philosophical domain, hence the thread being posted here. This means that he should get answers which could be accepted in the domain of Philosophy. If he wanted those kind of self-help tips or finance tips he would have formulated the question differently or maybe have gone to another thread. But for the way he formulated I am almost sure he wants one explanation that comes from one rational argument. Curiously you mention that The Secret has some philosophy. I will not give my opinion about that book and similar ones to not lose the charity or offend who might like it, but I suggest that you really research what place those kind of books occupy within philosophy or science, if any.
As for this thread, of course I can’t get solid conclusion in just one day. And make not mistakes, unfortunately until today I want a lot of money, I want financial success, that’s why I have been studying all my life and working insanely. But I believe this forum is not about giving us what we want, but reaching for the truth.
Now, for my temporary discoveries, I think two big topics emerged in this thread: financial success and material happiness.
Now, I would redundantly go back to what other off topic posters

already asked: the concept of material happiness. That is justified because you can’t tell someone how to reach material happiness if it means a different thing for different people. The OP kind of gave tips what he means by material happiness: having a good health and security.
Here comes the role of money and the reason why I think there are no philosophical bases or at least ethical bases in the context of his question (happiness :egyptian

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Cutting all irrelevant talk, I will accept just for the sake of this thread that financial success can be quantified, as emerged in one of the threads: one million dollars :hey_bud:.
In my view, there would be two ways in which you could get one million dollars: you become next Mark Zuckerberg and cash million dollars at the end of the day; or during your lifetime, summing up your humble wages in the end you have collected and spent with your health and security one million dollars.
The first option, suddenly millionaire, would fill pages, and unless you become the biggest philanthropist on earth, it reminds me of the parable of the rich fool (Luke 12:13-2). Quoting St. Augustine:
the farmer was planning to fill his soul with excessive and unnecessary feasting and was proudly disregarding all those empty bellies of the poor. He did not realize that the bellies of the poor were much safer storerooms than his barns
And OK, suppose that you would be indeed the biggest philanthropist on earth, how do you achieve that one million dollars? Unfortunately no general answer here also. People don’t give you money for nothing. You earn clean money in the context of mastering one professional area which people pay you for. And to earn a lot of money, I believe you have to be very good at that professional area and see what others didn’t see sometimes. This assumptions I make subtracting another elements that are beyond our control and that could condition such pursue for financial success (luck, influences, God?). Filling pages already, but in short if there is so far such unknown formula, which consider all these elements and would be obviously complex, it it worthy to spend all your life looking for it instead of directly seeking for what gives you happiness instead?
In my humble conclusion, there should be a simpler way to reach financial success (not the million dollar one). Live a life filled with virtues and with God. The rest, if it comes, it will come as bonus.