You should be able to do the job of an editor yourself. Read editing books, talk to other writers, do research on the internet, even take a class. But you should be able to do it yourself. It bugs me so much when people tell writers that getting an editor is an expense that they would have to endure because it's NOT. A decent writing teacher or person with experience in the industry would encourage their students to do their research and learn how to prepare a manuscript themselves. You are a writer. Write. Learn your trade. Don't spend money on services that you can do yourself if you can teach yourself.
Now if you are going to self publish there is one thing I do recommend that you go ahead and do and that is get a professional looking cover made. If you have the skills to do it yourself then save yourself the money but if you're like me and do not have the skills or equipment to do it then look around on the net and pay between $50 and $100 for a good cover. I would spend good money on a cover because people really do judge a book by its cover. I've seen far too many shitty ebooks out there that have covers that look like they were made in MS paint. Get something that looks so good it would not look out of place in a real life bookstore. Get something you can be proud of.
As for the rest of the expenses of being a writer all you need is a computer and an internet connection.