Well, if parents are more interested than a kid, first they need to talk to kid about it, what he or she wants to do and to learn and only then thinking of hiring a tutor. Don't you think so? If they don't, I'm more than sure such kids would rather pay for an essay
than do it themselves.
As to explaining parents all ins and outs of tutoring, just tell it as it. As you said, you've been tutoring for some time, you've got the experience, so tell parents how you do it.