It's easier to accumulate a million dollars net worth if you're two people rather than one, and owning real estate is expensive, and most people are more attractive potential spouses if they have wealth, and having children is expensive, so it's not surprising that these things are correlated with wealth. But that doesn't mean getting married, getting a mortgage, and pumping out a few kids will help you get rich.
I would say that to the contrary, getting married to someone you love, hoping for kids, and looking forward to getting a mortgage then be mortgage free are the simple yet overlooked steps to wealth. You can do those while working on a startup, at a startup, or at an established company if you have the right priorities: dont bother with what other people think about anything you dont have for sale, be frugal and hustle.
