Making money on the internet is not quite as easy as it is sometimes made out to be. But there are some who have been able to crack it and start making money online within a 3 month period. It has taken me much longer than this. Personally, I started an affiliate marketing website business whilst I was still working full time.
So I was not able to dedicate a lot of time initially to adding content and building authority. It took a good 8 months before I started to get some results. I am now into my 14 months and I am generating reasonable traffic through my site/s and some income from that. Nothing like where I expected to be right now, but it has been a factor of my input. I am working full time now at home, but i have several business interests outside of online marketing that take up a bit more time than I like.
So the short answer is, that how long it will take to earn is dependant on the amount of effort that you can put in. But also note that quality is a major factor as well. I can tell you now that I was lured into some free, and some paid, traffic building sites that I put a lot of effort and money into, only to find that the traffic I got was crap and it did nothing for my 'Google credibility". So it has taken some time, and lots of good quality, targeted content to claw that back.
But also note that I have a 2 year plan with this business to make it work and whilst I had a slow start, it is getting back on track with the plan.
Also, choose and online business that has exceptional, thorough training and responsive support and you will get there heaps quicker. Check this article
Hope that helps ,