Cheap Hub Motor

Complete kits start at around $400-500. Do you have the batteries? I doubt you'll find one that low $$. Good luck post what you find.
Hub kit

I just bought a hub kit on ebay for 399.00 and it works great. I got a manual for it. Its a wilderness energy hub bl36 brushless. Prices are coming down but i doubt you find anything as low as 50 dollars. They have a replacement hub for sell at 299.00. By the way i saw your age. Welcome to the real world anything tech worthy is expensive.