It depends on a lot of circumstances for example:
1. How old are you now?
2. No penalties for returning to work since you weren't old enough to draw from traditional retirement benefits anyway.
But let's just say you are 22, that will make the numbers easy. And let's say 70k is enough for you to live comfortably and you would be happy. Divide that into monthly income.... you need 5833.33 a month, let's just call it $5900 of residual monthly income. That means *each year* you need to add $590 of monthly residual income to your name to get there. That's doable if you focus your energies on truly *residual* income that will keep earning.
So, let's say you decide to make the internet your game. Each year you add a niche website, write 300 quality articles (less than one a day) back link them from quality sites etc. and build it up. You garner advertisers or use google and you average $2 per article per month. That gets you there. Do it every year, interlink the sites to add page rank, keep the content fresh, and you can quit your day job at 32.
Want to do it with stocks? Well that's a little tougher. But you can find 3% dividends. So let's focus on that. To accomplish the same goal you would need to accumulate 2.33 million dollars in relatively stable stocks that give a dividend payout. That would ensure you get your regular income but also have (if you invested well) a growing value that would keep up with inflation or better. Divide that by ten and you need to sock away 233k a year... yikes.
It's all math and that last example especially probably isn't the way to do it with stocks. (Buy value stocks low and sell them after 7 years when they are high for example would be better usually) But you get the idea. Set your goal, do the numbers, divide it down to manageable chunks and get it done.
Hope you make it!