I have found online editorial services for 13 to 14 cents per word, and that's cheap. Many online services use a method called Track Changes, and everything is handled electronically through email exchanges. I offer my own Rock Bottom Editing on this site for only $2.00 per page using that same method, which you may want to take advantage of. Older editor's do not use computers, but prefer to print out the manuscript and use the shorthand symbols for which they can and should provide a key to you upon delivery. There are usually no second draft edits. Once you receive the edited manuscript back, it is up to you to make all the suggested corrections. You will not and should not expect a finished, completed manuscript from an editor for hire.
You do the math and decide what you can afford. Is it really worth the investment? Well, if you want to be taken seriously as a writer in the publishing industry, the answer is yes. However, there are ways to get around the cost of editing. Ask your writer pals to read through the manuscript for you and mark their edits. I'm not talking about critiquing here. I'm talking about a read through for grammar mistakes and obvious issues. These 'friends' need to be objective, not your parents, your sister, your brother, or even a bestie. A writing group is really great for this type of thing, but you will need to offer them something for their time and effort. This is where a fair trade deal, the barter system, comes into play. You may need to be willing to mow a lawn, trim hedges, wash a car, offer the same reading of their work in return, or offer a free copy of your book once it is published.
Be aware, your manuscript may require more than one type of edit. This is why networking with other writers online is imperative and essential to your success as a writer. These online buds are virtual pals only and basically low risk. You should take full advantage of whatever they are willing to do for you in exchange for the same effort. Content editing is equally as important to help ensure your manuscript is consistent with certain time frames, the hair and eye color stays the same with each character throughout the book, descriptions and details of certain areas, backyards, schools, parks, police stations, houses, bedrooms, living rooms, restaurants, gas stations, etc. are consistent throughout.
Either way, you need to make sure you get, at the very least, a thorough basic edit before turning over your manuscript for review by any publishing house. This will save you and them a lot of time and money later.