I recommend a detector made by White's. I own two that I have had for nearly 30 years and still work great. They are the 5000D Series 2 models. A good discriminator helps to avoid junk. But, for 9 year olds nothing is junk. A decent non-discriminating detector can be had for around $150 or so. Don't buy Bounty Hunter or Jetco. Get something made by White's, Garrett or another well made piece of equipment.