It is always a good idea to have an extra pair of eyes look at your writing. You may want to start with a friend or family member, but it will make sense to hire an editor when you are ready to sell your ebook. Unlike traditional book publishing, where there is an editor on staff to oversee your final draft, when you write and market your own ebook this task is left entirely up to you.
Make sure to find someone who has edited many books during their career. A good editor can spot things in your ebook manuscript you may never have thought about. Contact me if you have writing that needs to be edited.