For me, it's kind of hard to say. I wouldn't call it "broken" because of the nature of the game - the player for the most part has the power to adjust things the way they think they ought to be. But I will say it doesn't seem like much thought was put into the economical side of the game.
It's "easy" to make money in the sense that it's hard to ever be dirt poor to the point where your sim is living paycheck-to-paycheck unless you're heavily restricting your gameplay or handicapping yourself. Yet, at the same time it's hard to get your sims rich enough to the point where they could buy a mansion during their lifespan if you wanted them to (unless you're doing something exploity.) Sims at the bottom of their careers experience no struggle and sims at the very top don't make what they should be making.