Learning to code without a computer is what we all did, 40 years ago!
He may write programs on paper, and send them to you to type them in, compile them, and print out a listing with the errors. You then send back the listing, and he will correct his program and repeat.
He'll become a great programmer, since he will have to be extra careful to avoid losing one week on some typo.
Now, it's been a few years since gcc has been able to produce a real listing of the compiled source. You would have to write some script to combine the error output with the source file to produce a classic listing. Similarly for other common modern programming language implementations.
On the other hand, without direct access to a computer, he would not attempt to write any interactive or GUI application, only batch programs, unless the interaction is performed only by an external tester for him.
Another idea: some progress has been made on optical character recognition, so if he can write well enough, it may be possible that you may be able to scan his written programs, and convert them to source file easily, without having to transcribe them. So the process could be smooth enough.
If writing ustensils include typewriter, then even better for the OCR!