Updated: Nov 13, 2019
I'm going to be totally transparent here. You can publish your novel for under $200 with Amazon's Kindle Direct Publishing platform.
Premade cover: $100
Book formatting: $25
This way you will have a book. You will probably sell a dozen or two copies in the first month. For many people that is enough to feel like they are real authors.
Ideally, you have a circle of good writers for critique partners, a group of great readers who give amazing feedback and spread the word, plus a friend who's an English teacher and will proofread for you. The more time, expertise and effort you put into your book the better it will be.
Please note, if you are serious about selling more than friends and family you need to market your book. And if you want your marketing dollars to go anywhere you need a professionally edited book with a powerful cover. It is completely possible to make your self-published book just as polished as a book from a big publishing house. It just requires the help of a few experts.
The most preventable mistake I see is new authors trying to make their own cover. Graphic design is an art and a science, and can't be conquered in a day or a year. Your cover is the most important ad your book will ever have. If a quality custom cover is out of your budget, there are great premade cover sites for most fiction genres. For less than $100 you can get the benefit of years of expertise.
Do you want a book signing at a local bookstore? Would you love to build an author platform or win writing awards? Maybe you want to record an audiobook or sell to libraries. For those goals, you need better tools, like a complete custom publishing package.