Anyone who's tried to build something knows that you need the right tool for the job. And those people usually also know that that tool is not going to be the same thing for every single thing that you want to do in your build. But money isn't really a tool...at least not like a drill, or a toaster.
For a lot of things that involve money, time is involved somewhat. You trade you labor in units of time for money, and often you can trade time and money for each other, like hiring someone to clean the house so you get that time back, or being the one to clean the house so you can get that money. So with this in mind we just need to figure out What Time Is, and we'll know right!
Ok, so maybe that didn't quite work, but what if we focused on that time -> money transfer. The trading of labor. Time isn't really of value to things that don't perceive it, and so far as we can tell those are just us animals. And this suggests a look at one of my favorite trios: The Means of Production.
But before we go there, I must point out that that's just half of the story--the production half. The other half--consumption--has another story, which is Why We Need Money At All.
So choose your own adventure time:
The Means of Production - money and production
Why We Need Money At All - money and consumption