By working with a professional with years of experience and in-depth knowledge of online marketing specific to the types of products and/or services you promote would be highly advantageous. Additionally, we suggest you consider a person that has traditional marketing and advertising experience as well as knowledge of online strategies.
Before deciding on just one person, it would be worth the investment of time to get in touch with the professionals that made your short list. Having a conversation, preferably on the phone would give you the opportunity to ask questions and get a better feel for the person's level of expertise. At that point, you would be able to choose just one internet marketing mentor that you have confidence in so ultimately, your online business would outsell the competition.