There are a number of Internet sites that invite you to submit material and, in some cases, indicate that you will be paid for the content if it is popular with site viewers. One of these is Helium.com. Let's take a closer look. First, how much will you get paid? Here's what they say:
This is the best part. Sure, Helium is an outlet for the writer in all of us, but it is also a place where you can earn not only the adoration of your peers, but money, too! We want you to be part of the success here. Helium shares a portion of revenue with you. Every article you write is an asset which can earn you revenue---into perpetuity. The better you write, the higher you rank, the more your reward.
Yeah, but how much? I can't find anything more specific on the site. (If I've overlooked it and you have found it, let me know). I'm guessing they can't give you any numbers because this will apply only once they have revenue. They could tell you now what percentage of their revenue they will distribute, but even then your share would depend on how many writers got a cut. So the answer is: nobody knows. If you're comfortable with that, no problem.
However, what kind of rights are you granting them? If you actually read the 'terms and conditions' (which I'm thinking probably few people do), here's what you find:
You grant Helium, and its affiliates, a worldwide, perpetual, irrevocable, royalty-free, transferable, non-exclusive right and license to use, copy, modify, delete in its entirety, adapt, publish, translate, display, create derivative works from and/or sell and/or distribute content posted to Helium.
OK, at least it's non-exclusive, but even so, they can do whatever they want with your material. If they put it into a book, for example, you get...er, nothing. Ever. World-wide.
Let me be clear: I'm not accusing Helium of doing anything underhanded; if you agree to their terms, that's up to you. But I do say: writer beware. Always read the fine print, so you know exactly what you're gaining (if anything) and what you're giving up.