I'm not into the show arena or papers but I did get a registered Nubian buckling this year....to improve the does I have in the future...
In looking for a good homestead goat....I strongly suggest going at milking time to check volume and disposition...as well as "healthy" appearence. The seller should be knowledgeable and provide you with feed info., worming schedule, and be able to tell you if said doe kids easily and mothers well, is aggressive or has been tested or not. Most folks w/ registered animals have their ducks in a row...and will offer loads of info. and advice.
It is possible to get unpapered animals that were culls from registered herds...I have one...bought in milk for $75 6 years ago....she was very wild and not easily milked..now the herd queen and very good milker(1gal plus) just tiny-teeted

She was bred twice to reg. Nubian buck (rented) and last year I kept back a buckling of hers to breed back...she had a daughter

Daughter looks like mom (alpine some toggy) but is growing fast and has larger teets like nubian....so I'll call it line breeding instead of inbreeding
I didnt bother doing any grade paper work from previous breedings either...just not worth the bother....but for me it works

I will be selling(or trading) the buck as registered when he has completed his service here in a couple of years....