You can earn unlimited money by selling ebooks. You want know some basic knowledge in this field.
1) how to write a book
2) Basics of Payment gateways
3)How to market your ebook.
If you know these three basics, your ebook work as a money making machine.I will describe these three basics.
1) how to write a book :-
First step of writing ebook is finding contents. First research about your contents. You can read online contents and offline contents (books). Never copy contents. You can write in your own words. You can use images and schematic diagrams if you want.
Open word document and write your content as professional writer. You can also use Google Drive for writing content. You must add header and footer with title and page number. Add your ebook name and cover page in first page.
Then convert your word document to pdf. But you can download as PDF file in Google Drive.
2) Basics of Payment gateways
You need a PayPal account for it. Your ebook automatically download after payment. It is very easy. First setup account here. Then go to Create New Produc > Then upload your PDF. You must add your PayPal email ID.
3)How to market your ebook
First make a blog or website for marketing your ebook. You can use weebly.com , WordPress or blogger. Then write about your ebook and do SEO (Search Engine Optimization). You can also increase sales by Social Media Marketing. Just Google "Dofollow website list" Then create account and post about your ebook.