If we are talking strictly about ability, then 9 years old is certainly not too young for a kid to have their own computer. After all, in this day and age, children are usually quite experienced with electronics a lot earlier than our generation was. The decision whether or not to spend the money to get them a brand new iPad or Chromebook should come down to whether or not you think they will benefit from it.
Remember, technology like iPads & laptops can be much more than mere entertainment devices, especially if parents take the time to help set everything up.