Recently, I have been browsing writing jobs in several renowned freelancer sites, and I often come upon cheap propositions for ghost-writing a series of books ...well if you like working for peanuts. I feel I can come up with a series of books, but what do they do afterwards? How can you market your own work?
Reach out to book bloggers and offer them a free copy of your work in exchange for an honest review. If you have a series of books, offer the first one for free on Amazon whenever they allow it. This is an easy way to capture sales for the later books. You can also arrange a blog tour in order to promote your work, but if you are completely unknown you may have to pay for it.
Get involved in the community of authors and readers online. The challenge of self-publishing is always to get your book in front of it's audience. If you have a relationship with other fans, it's easier to do this.