Most definately. Thats what martial arts is all about. This is a little bit of a poem that i think sums it up perfectly. "If you meet a Student and you know he is an evil person; then you would not teach him even for 10,000 pieces of Gold. And if he is not Righteous and has no Honour, You would not teach him even if he were your Relative. But if he is Righteous and has Honour, You should teach him even if he is a Stranger to you and has no Money." So yeah, i think you should let him train for free. Maybe he can help you out in some way to repay his training, or just let him pay later on, or just give whatever he can.