A lot of writers feel the need to go to freelance editors and spend a lot of money, but it’s not always the best thing to do. It depends on exactly what kind of editing the editor is going to do for you, and it’s also important to make sure the editor is going to be available through the entire publishing process. For example, what if you hire an editor to help you develop a proposal and manage to sell it, but then the editor isn’t involved in writing the actual book? If there’s a big change in the writing between the proposal and the actual manuscript, the acquisitions editor isn’t going to be very happy about that. I’ve heard of books getting canceled as a result.
You also need to make sure you actually need the kind of editing a freelancer editor can provide before you spend thousands of dollars on it. Most agents today are doing a lot more hands-on editorial work than they have in the past. If you can find an agent who will help you do that work, obviously you don’t need to pay a freelance editor to do it. And once your book has been sold, an editor at the publisher may do some work on it—although not all editors at major publishers are doing that kind of editorial work anymore.