A colophon page is the contact page of your book. In this article I tell you what you should and can put in it.
The sale of your book starts with a good blurb. To write a blurb is even more difficult than the first sentence of your book.
Writing your story is free. Publishing your book... not. There are one-time costs and recurring costs. Learn all about it here.
Books that you buy in the bookstore have an ISBN. Learn all about ISBNs. Like when do you need one, how do you get it and what does it cost?
When your book is published, it is of course the intention that it sells. Learn about what you may need to promote your own book.
You have set up a company for self-publishing. But where will the money come in, your own account or perhaps a business one?