Apple account

This article explains how:

Family Sharing and Apple ID for your child - Apple Support

He won't need to already have an email adress created to make an apple ID.

I would recommend to reset his phone when switching him over to his own account. to make sure you remove all traces of you apple ID:

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

You can also just sign him out. but keep in mind that all the apps he currently has will then be linked to your apple ID, and will require your password to be updated.

Good luck!

You have to set up Family Sharing to create the ID. Once you do that, he should be able to use apps purchased with your ID without requiring your ID and password.

Family Sharing.         

Family Sharing - Set up.     

If you don't want to fully reset his device, when changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing between the IDs to keep access to your apps/purchases. 

Set up - your child’s iPhone, iPad, or iPod touch 

How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.        

What to do after you change your Apple ID or password - Apple Support.     

You are welcome.