Is Nylon fabric water proof? or are all the nylon products for sale treated with something to make it water proof? If so, what is that product? Would it work on other cloth materials?
It has to be treated with a waterproofer. There are quite a few out there, some of which will work on many clothing types. Most of these products have to be re-applied on occasion as well.
Look up NIKWAX. It's a line of wash in water repellent. They have some for natural fibers like cotton. They also have stuff for nylon and goretex type stuff.