In response to money-grubbing coaches, you need to do your homework on any professional that your kid is going to do extensive work with, be it a doctor, tutor, or coach. Richard Williams did a phenomenal job with his girls, but without Rick Macci's experience, training and knowledge, they wouldn't be where they are today. Good parental help is fantastic, and if that parent is a world-class coach then that is a great asset.
The work being put in needs to equal the goal. If you want to play D2, D3 or NAIA tennis, then being an after school player for 2-3 hours over several years will probably suffice with the right amount of tournament participation, coaching, etc. If you want a good D1 scholarship to a quality program you better jump in with both feet.