>>A friend of mine has written a guide for mycheats.com and wants to continue a possible career in that area. What is the best way to start it?
He wants to write game guides? And he needs you to find out how to go about it? How old is he?
>>Where are some other good sites that do freelance writing for games?
Your question is not understandable. Read http://www.sloperama.com/advice/lesson32.htm
-- actually, have your friend read them. Let him do his own career research.
>In fact, no one will pay for a writing, except you are writing a book to be sold.
That is not true.