Zappers are good but Rife really is better. If your friend can afford it, he might want to invest in a machine of his own. It can be very time consuming and being in the comfort of your own home, on your own schedule, can make a huge difference. Especially on the days when you don't feel worth a damn!
I've had a GB4000 for about 4 years and it might be the best money I have ever spent. Right now it needs a tune up and some updated frequencies though... I was a little rough on it : )
I wish your friend ~all the luck~ on what might be a long road to recovery. He's is lucky to have such a good friend as you in his corner!