This will depend on budget and the quality of your writing. Some authors can get fairly close to a polished manuscript on their second or third draft, and this reduces how much work needs to be done by various editors.
Editing costs money. It’s an important skill, and almost an art form of its own. Developmental editing, line editing, copyediting, proofreading… not to mention designers, formatters, indexers, and beyond! It can be a hefty price tag if you’re self-publishing, especially if you are relatively new to the publishing scene.
If you are strapped for cash and want to maximize your investment, I usually recommend that authors get at least one round of copyediting done, and then one round of proofreading. If you can only have one, then go with copyediting. It’ll be the most valuable return on your investment. The more self-editing you can do, the better.