…but, can you afford to produce a book full of errors? If you really don't have the cash, then you should probably be sending queries to various publishers rather than trying to publish the book yourself. If a publisher picks up your book, they'll pay the editor, but if you are determined to self-publish and you decide to do it without an editor, you may come to regret that choice.
Self-publishing is a business, and if you hope to succeed in it, you have to manage it like a business. You have to look at your skill set and decide which of the many tasks associated with publishing you are suited to doing yourself and which can be done more effectively and more economically by others. Your time has value, and you have to decide how it is best spent.