Thanks to online sites like Amazon's Kindle Direct Publishing (KDP) and CreateSpace, as well as Smashwords, Barnes and Noble, Kobo, and others, an author can self-publish an ebook and a print-on-demand paperback without spending a dime. Before you get to that point, however, you will need to spend money for Microsoft Word if you don't already own the word processing software. Most online self-publishing sites prefer a Word file, which is then converted into other formats by the sites' conversion software. Smashwords, for example, uses software they've named Meatgrinder to convert your Word file into pdf, epub, and Mobi formats. KDP's software converts your Word file to a Mobi file that can be read on any Kindle, while CreateSpace uses your Word file (copied and pasted into a template in the size of your choice) to print paperbacks on-demand.
Unless you're a graphic artist or have a talented one in the family, you'll need to spend money on a book cover. Several online sites offer pre-made covers for ebooks, and for an extra charge, the artist will create a matching spine and back for your paperback edition. KDP does offer authors the ability to create covers themselves, but as I said, you need talent. If you don't have that, then you need money to pay talent. I recently bought a very nice ebook cover from selfpubbookcovers.com for $75. I also have a barter arrangement with Bill Wilkinson, a British author/graphic artist. I edit his books for him and he creates covers for me. He can be reached at format-your-book-4u.com.
Speaking of formatting, some authors prefer hiring someone else to render their manuscript into a form that will be accepted by Meatgrinder and other conversion software. However, it's not that difficult. I highly recommend The Smashwords Style Guide by Mark Coker, the founder of Smashwords. I followed his advice on creating styles that I then applied to my first manuscript, and when I submitted to Meatgrinder, the file converted without a hitch to formats that could be read by every ereader currently in existence. I took that same file, made the necessary changes to the front matter (for example, changed "Smashwords edition" to "Kindle Edition") and submitted it to KDP. Again, the file converted with no problems. I then copied that same file into a CreateSpace template for a paperback.
The most amazing thing about The Smashwords Style Guide is that all the valuable advice is FREE! Mark Coker has also written other free ebooks on marketing books and on ebook publishing in general. They are invaluable for anyone just getting into self-publishing.
Finally, if you know or suspect your spelling, punctuation, and grammar skills aren't the best, you need to hire an editor. The most common objection to self-published books is lack of editing. When a reader opens the Look Inside feature on a book retail site—or worse yet, pays good money for a self-published book—and finds it loaded with punctuation, grammar, and spelling errors, it hurts all self-published writers.
I’m not talking about one or two mistakes. No matter how often you look at your writing and no matter how many other pairs of eyes look at it, something will slip through. Our brains see what they expect to see. A sharp eye will likely find an error or two in this post. But it is our duty as writers to minimize mistakes.
Ideally, you also need a content editor. A content editor focuses on things like plot holes, poor character development, etc., and may or may not point out your grammar errors along the way.
So what do you do if you have written a book and have very little money to spare for the things I've mentioned above? First, if you don't already own Microsoft Word, you can get a monthly subscription to Office 365 Personal Edition for $6.99 a month at https://products.office.com/en-us/office-365-personal. This gives you access to all of the Office software, including Word, as well as automatic updates and bug fixes.
If you can't afford a graphic artist and even the pre-made covers are too expensive for your pocketbook, ask friends and family. If none are any better than you are, check with local high schools or colleges. You might find an art teacher or art student who would be willing to design a book cover for you in exchange for the credit at the front of your book. Art students need examples of their work for their portfolio when they go out in the "real" world, so they may be willing to design a cover for free or for very little money. Know that you may have to pay for any stock images they use in the design.
As I said, if you follow the advice given in Mark Coker's free style guide, you won't need to hire a formatter. Beta-readers (people who read advance copies of your book and give you honest feedback on what is good and what needs to be improved) can often serve as free content editors, and depending on their own skills, free proofreaders. You can find beta-readers on sites like Goodreads. And again, check with friends and family. Nearly everyone has a cousin or friend who aced their English classes. Make use of them.
And when a reader contacts you to tell you about boo-boos they noticed, thank them profusely for their help. One of the many benefits of self-publishing is that we can make changes any time we want.