I have been a freelance book editor for 26 years, editing more than 600 books on every topic under the sun. I have edited academic and professional books for traditional publishers, as well as nonfiction and fiction for publishers and private authors. I am a native English speaker. During my editing career, I edited a lot of self-help books (see the list below). It sounds as if your author is not a native English speaker, so my rate for editing and rewriting ESL books is $70 an hour. That comes to $700 for the 5,000-word portion of your project.
Samples of self-help books edited:
The Paleo Diet, Cordain, Wiley & Sons, 2010
No More Fatigue, Challem, Wiley & Sons, 2010
The Food-Mood Solution, Challem, Wiley & Sons, 2006
Knockout Workout, St. John, Wiley & Sons, 2008
Commitment and Healing, Isay, Wiley & Sons, 2005
Fit and Female, Coopersmith, Wiley & Sons, 2005
The Hamptons Diet Cookbook, Pescatore, Wiley & Sons, 2005
Every Woman’s Yoga, Prima Publishing, 2002
Staying Power (fitness), Wiley & Sons, 2004
Calm Mind, Fearless Heart, Seaward, Wiley & Sons, 2004
Still Procrastinating? Ferrari, Wiley & Sons, 2010
Retool Your Relationship, Dolenz, Wiley & Sons, 2010
Don’t Miss Your Life, Robinson, Wiley & Sons, 2010
Let Love In, Brendt, Wiley & Sons, 2009
Heal Your Aura, Carol Publishing, 1999
Never Get Angry Again, Lieberman, St. Martin’s Press, 2018