before the modern age? you are thinking roman empire or so? you could simply NOT make money back then. you were rich or not. you could not change what you are back then. Now you can, and this is the greatest difference.
Actually, something did change... in the last 10 year. The Internet. Information freely available, venture company can be created with almost no investments. That gives a whole lot more of people a chance.
To GabeCohen: as you said ... inheriting is a sure way to get money. but not a steady way to make money. unless people keep dying around you.
To add to my previous answer as well... of course Investment and partnership might grow your wealthiness if you do the correct moves. but you asked for steady income. so I keep my answer everyone needs a job until you've reached financial independence and really secured enough money to work strictly on your investments.
One good thing to do is to increase the number of revenue source. Not simply thinking about ONE source of become millionaire. but having many little investment increasing your income. Like transforming a hobby into a profitable business.
I would stay away from those clubs filled of people who wants to convince you to invest in their things. Pyramid marketing and other Get-Rich-Fast scheme are also usually risky, totally illegal or simply fake.
Think by yourself. reduce your expense, decrease your life style. make investment, not luxury spendings. build up a security fund so that when something happen you can live 3-12 months without a job or anything. this is not they money you will want to invest. this is just a security fund for you and your family to not have problem. only this give you the freedom to then do what you want with your extra time and money.
It all also depends with what you want.