Well that really depends on what college you are planning to get your child into and the study habits/work ethics of your child. If you want my honest opinion, I don't think that college consultants are any more help than just looking up how the college process works online and then encouraging your child to do all those things. Yes college consultants may know a few things that aren't covered in some online websites, but those few things can be easily found if you use more than one website.
I also found it more helpful to actually talk to people who are studying or have studied at the certain colleges you want your child to apply to and admissions counselors from those colleges. They know much more inside details about that specific college than any consultant would because consultants are meant to just help you through general processes that are just as easily found online while students and admissions counselors know more about the specific schools. You can try doing this by contacting the admissions office at the college your son is applying to and asking for an appointment in person, via phone, or whatever.