Many people offer reprint rights on their articles now a days, and these can dramatically speed up your mini e-book development time by giving you content that you didn't have to write to use in your book.

It takes a bit of planning, in most cases, but you can follow some proven steps to get yourself in a position to compile a set of articles into a mini e-book.
Your first step is to find high quality content, within your niche ? there are a tonne of article directories out there that bring together quality content in one place. Browse them for content that would fit with your e-book and choose your articles carefully.

Once you've chosen your articles, you'll need to contact the author of them, and ask permission to use these articles in your e-book ? some authors give limited rights on their articles ? others don't mind what you do, as long as their bio and/or byline remains intact, so you'll need to gain permission from them ? and if you can, offer them something more than getting their name out there. Though it may be good for their profile to take part in this project, some authors like to have 'more' out of these offers, so its something you may have to consider. What that 'more' is depends on what you need from them.

Once you've gotten permission, you'll need to plan what unique content you'll be adding yourself ? if you're planning on selling your mini e-book you'll want to add at least 50% new content, or people may complain.

Alternatively, you can use these reprint right articles on an auto responder or mini e-course, to promote your e-book. Instead of writing the e-course yourself, you can use the reprint right articles to add context and content to your e-course and offer a link to your e-book within the message.

Either of these outlines above make using reprint articles a viable and solid income generator for anyone starting to compile or create e-books.