Perhaps for most people who are looking to make money online, preference is to spend as little money as possible, or preferably even not spend any money at all, and still earn a good full time income. In most cases, this involves spending time over the computer to achieve these results.
There are many many ways from selling products on ebay to Amazon, to creating applications for sale. I'll just name a few avenues that the masses can try.
1. take online surveys - But be warned.
Some companies recommend that you can take online surveys and get paid for your time. From my experience, this is not the easiest way to earn a good, stable full time income. This is because you could spend alot of time trying to find the right companies that actually do pay you for your opinion, but the chances of succeeding is not high. For every company that you do sign up with, probably you will get offers or discounts and coupons instead of actual monetary benefits.
Of course if you decide that this is something you're comfortable with, just be sure to use a separate email so that the many offers you will get are separated from your daily mail. The time and money earned ratio is not the best.
2. Google Cash methods
This is a method that made those who knew how to do it very rich in the years before 2008. Before this time, Google was not policing Adwords much. Adwords, for those new, is a platform where you can advertise ads for a fee. The lowest click you can pay for each click is $0.01. The highest, also known as the Google Slap is $15.00. In this case, you act as a Traffic Broker and funnel targeted traffic to relevant offers and earn a commission when a sale or action is taken. This method can still be used today, although its not as easy as it was before because of new Google Adwords Policies and alghorithms.
Some ads lead to affiliate products which pay the "broker" who sent the traffic a commission. This is called affiliate marketing, simple and easy once you learn how.