1. You'll get writers that re-write for <snip> page/article. But do not expect them to be the best. They are ok for 're-wording' articles.
2. For <snip> page you can get reasonably good professional writers.
3. Test the originality of the content from time to time using copyscape.com. You may land in perfect trouble if you are using copied content.
4. Test the new writer with a test project first; before giving the bulk of work. Pay him for the test project.
5. See his work samples.
6. Prefer the ones that are in trade for more than 2 years.
7. Avoid students at all cost. They vanish suddenly during their exams.
8. Sign a non disclosure agreement with your ghostwriter. He should keep the project details secret.
9. Prefer writers from Kolkata, India. Kolkata (city) has the best writing talents in India.
10. Prefer to pay fees over <snip> in installments rather than as one down payment.
11. Keep an option to come out of the agreement at any time.