Copy editing is not exactly the best job (return wise) you can do online. However, if you have good command over your language - mainly English - but not very skilled in any particular domain you can start making money working from home via this method.

To start working online as a copy editor you don’t need to have a degree in journalism or related areas. Online copy editing jobs are offered to virtually everyone, though newspapers and magazines vastly go for those who have relevant qualification and experience. But there are hundreds or thousands of websites that need copy editors to carry out their editing needs that include news letters, eBooks etc. Once you gain experience you can even go for a real press-related copy editing job.

Where to find a job?
The following are some of the sites that offer copy editor or proof reader jobs online (Not all may have immediate opportunities)

Elance - Click ‘Copywriting’
ProofReadNOW
Guru.com

You can Google out a lot more of them.

Tips
. Try to understand your customer needs – You need to distinguish between the requirements of your US customer from that of a UK one due to difference in English language usages, spellings, grammar etc
. The consistency of formatting, proper punctuation etc have to be maintained
. A fair bit of understanding of HTML will help a lot
. Read through your copy edited text several times and even better, get it read by somebody you know, to avoid any silly mistakes

Happy job hunting !