Self publishing today isn't the same as it was even three years ago. If you choose the self-published option there is no reason for you to spend hundreds or thousands of dollars to put your work out there.
Amazon has a wonderful option called Kindle Direct Publishing, also knows as CreateSpace. Publishing with Amazon is free. There is also Smashwords and Barnes and Noble's Pubit site. You don't need to spend a ton of money to get your book out there. But should you self publish your book?
There are many self published works out there that are terrible, there are also some great books. What makes a book terrible? Either the content or the condition of the language. Content problems are more difficult to fix. The condition of your language or grammar is much easier, but still a huge tasks. If you are one of those people who scored all F's in school in English Literature and Grammar then putting your work out there without a professional editor is a mistake.
Not all professional editors are created equal. Some are good, others suck. How do you know who to go to? Word of mouth. Talk to writers and find out who has helped them. Learn from others and use their experience to help you along. Get quotes from multiple editors and go with someone you trust.
If you book needs to be edited for content, that is much more difficult. At some point you need to listen to what others are telling you about your book. Join a critique group and really listen to their critique. Not all critique's are solid though. I've had the rogue critiques that were totally off base. Know your audience and study other books in print.
Things to pay attention to. The time line of your story. I've read self published works that terribly mess up the time line. By the third chapter I'm so confused because the author hasn't kept the time line straight. If your book starts on a Thursday don't make the next scene the Wednesday before unless you do a flashback, which isn't recommended. A good way to lose readers is to confuse them.
If you feel that you can work out the kinks of your novel, then do so and self publish. If you are new to writing, do everyone a favor and find someone else to edit your book for content and grammar.
Publishing by yourself does mean that you will be doing all of the advertising. You won't be able to tag along with other books from the publisher, because there are no other books. Once you build a solid foundation with ten to twenty books then you will have a built in readership, but between now and then you will have a load of promotion that you will have to do. Authors at large publishing houses also have to advertise, but they do have a bit more backing to build them up and help launch the book.
So does that mean you need to hire a publicist? Not necessarily. Social media and word of mouth helps to sell your books. There is also a great deal of luck involved too. Either way you will be required to do hard work. Going with a large publisher will get you more money up front, but it could also stifle your creativity and your productivity.