Lets say this money is actually in the most convenient form - your checkings and savings accounts. No real investments. Lets give you a comfortable 150k/yr interest-only income. At my bank's checking/savings rate of 2.25%, you need $6,666,666.67 stuffed in there. So, $6.7M. To pull that off, you'd need to put away $150k/yr for 44.5 years. But that's all you make, so you're going to need to go for 89 years since you can only really put away like half of that. Lets say you don't hit that $150k/everything paid off mark until you turn 27. You can retire at age 116.
Yes, there are some logical holes in that argument there, like "why do I suddenly need to double my income after being alive for 116 years?" - but I'm tired.
You need a lot if you're going to invest casually.
A good rule of thumb is that 5% investments are easy to come by - CD's and such. So to pull 1M/yr at 5% rates, you're going to need 8M to start with. Which really makes you wonder... "why the hell do lottery winners ever run out of money?" 1M in a 5% investment will pull you a cool $50k in interest - which should be more than enough to retire on, and 1M is a very attainable goal for many, many blue collars, and easily reachable for white collar.