Here is my 2 pence/cents/euros/etc worth
In my experience writing has been that it is one of those things that you hate with a passion when you have a deadline looming, but it does feel pretty good to see your work in print, so overall it is a lot of fun.
Money-wise it is not great. It is nice to have a bit of extra cash on top of a regular salary, but it certainly would not be enough to live off. As Peter said it is not a reason to write.
As for finding information, most of the stuff that I have writen has come from my own personal knowledge and experience in the world of IT. We certainly did not receive any help from Sun with the content of our certification book, and tried instead to write a book based on how we learnt for and passed the exam.
The Java writers forum that was mentioned is very good for asking new author type questions as everyone there has been through it at some point
Cheers
Sam
<a href="http://www.samjdalton.com" target="_blank" rel="nofollow">Sam Dalton</a>,<br />Co-author of [http://www.amazon.com/exec/obidos/tg/detail/-/1590592255/qid=1068633302//ref=sr_8_xs_ap_i0_xgl14/104-4904002-9274339?v=glance&s=books&n=507846]Professional JSP 2.0[/URL] (October 2003)<br />Co-author of <a href="http://www.amazon.com/exec/obidos/ASIN/1861007701/ref=ase_electricporkchop" target="_blank" rel="nofollow">Professional SCWCD Certification</a><br />Co-author of <a href="http://www.amazon.com/exec/obidos/ASIN/186100561X/ref=ase_electricporkchop" target="_blank" rel="nofollow">Professional Java Servlets 2.3</a>