Answer:
I am a portal to another world which you cannot enter. Only you can see me but I can't see you.
I may only be given but never bought. Sinners seek me but saints do not. (one word).
I get wet when drying. I get dirty when wiping.
I have a hundred legs but cannot stand. I have a long neck but no head. I cannot see and I help keep your house neat and tidy.
What has no beginning, end, or middle?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?