There is just no end of answers to this question. You could build a blog as an authority and ching from AdSense; you could sell eBooks; you could drop ship; you could build an affiliate site; you could build a blog reviewing stuff in a certain niche and affiliate link to those you review; you could write an eBook on "How to Make $50/Day on the Web" and sell that; on and on. I'd perry this and ask you what are you good at/interested in? There's almost always a way to turn a talent/interest into something you could do online at that level.
Well I used to try and make money from home but gave up in the end, I realised I can make much more from simply getting a propper job in web design, I get a nice salary now.
Indeed, salary is always nice . . . until change of management, downsizing, outsourcing or any one of a number of other things "pink slip" it. On the otherhand, being independent ain't easy either, but at least I know I'll never pink slip myself. However, looking to make an average of $50/day online is a very reasonable goal and I'm all behind anyone who would like to make a serious effort toward that, fully recognizing that it actually does take WORK ( you don't just throw up a site and make money ), and it will take time ( at least a few months to get SEO in order ).
I agree with gobbly2100. Once I was a freelancer, for about 2 years. And now I have a job with a handsome salary. However, I think what Sean@WMS said was right too. I'm running a website in my spare time, but I don't have enough time on it so I don't even think of making money. Anyway, it depends.