Bring it up at your next club meeting. Get the whole club involved. I,m sure someone has an old plane they don't fly anymore. I'll bet someone else might donate an engine or motor for the cause. You said you have a radio. You could set up a club plane he can learn on until he can save up enough to buy his own plane.

Also not to critize but why did you leave his side when he was just learning. If my instructor did that within my first 10 flights i would be pissed.