Hello, and welcome to the cafe
He may not actually need a tutor - fortunately there are literally thousands of tutorial videos online for all aspects of the program, and if he's only 12 he's got time to work his way through them for the 3-5 years it will take to learn the software to a professional level. Unfortunately the demo will run out after 42 days, so you should contact MAXON directly about getting him the proper student version.
But if you really think tuition is the way to go you should say if this is a paid position to avoid any confusion when people are replying. Typical tuition rates are around $70 per hour. If it is a paid position, I'll move this post to 'The Job Line' for you.
I'm in the UK, but do 1 on 1 C4D workflow training via remote screen sharing anywhere in the world for a £50 (UK) per hour if you would consider that. If interested feel free to PM me to discuss further.
CBR