On working as a freelance copy-editor in graduate school Is it advisable for a graduate student to work as a freelance
  copy-editor (for few hours a month, for papers in his/her area of interest)?


This topic emerged a few days ago during a conversation among a few colleagues of mine; we came up with the following upsides and downsides:

Upsides:

(1) increased financial independence;

(2) valuable training.

Downsides:

(1) possibly time consuming and stressful.


  Is there any other upside or downside we may have overlooked? (For
  example, could this kind of experience turn out to be a positive
  addition to an academic CV?)
Who says you're any good at it? Why would a colleague pay you for such a service when many lab-mates or other colleagues would do so for free or a promise to return the favor later? Who says anyone local to your area would pay you for such a service? Freelance implies not working for an existing service, so are you prepared to deal with the necessary tax implications of being self-employed (in the US or your country)?

I wouldn't expect this to appear on a CV, and I would find it strange if I read a CV with it this experience listed unless the candidate worked for a professional editing service (where it might be a plus for them).