How many drafts is enough to prepare a manuscript for professional editing? A first or second draft isn’t worthy of the investment, after all. A manuscript isn’t ready for editing until you’ve set it aside for weeks or months (to regain some distance and objectivity), sought out feedback from objective parties, and revised it thoroughly from the story level up. A professional edit before then would be a waste of time and money.
New novelists often come to me after three drafts: one to cover initial changes of heart involving the story, another after feedback from early readers, and a third to fiddle with grammar and spelling. That covers less than half the ways I recommend strengthening your manuscript before you seek professional editing.