Paperwork is only as good as the breeders reputation is. Paperwork does however give you the ability to take legal action though. I look for pictures of the parents and a picture of them locking up. A reputable breeder is the best as most aren't willing to tarnish the good name they have built for themselves.
As for selling, if I bought a 50% poss het Albino and tried to prove it out but failed to I would sell it as a 50% poss her but disclose that I was unsuccessful in proving it out.