Very rare
Are you certain that the pup is albino? Chihuahua's come in many shapes.colors and sizes. A true albino Chihuahua would be a concern. White along with many other colors is common though, with Chihuahua's being os common and bred so much lately can't really say there are particularly 'rare' or uncommon colors. The last show I was at there were at least two whites, long coat and smooth coat and others of course. Someone using the term 'rare' usually means a big red flag. Rare often means 'outside of standard' and 'not really supposed to be bred or bred for' along with other implications. There actually are no color disqualifications (nor does fault or disqualify actually always mean 'rare') in a chihuahua (recently changed I believe), they can be any color. With a true albino there would be some additional health concerns usually. Here is the breed standard and the breed parent club (the people who set the standard, AKC doesn't do that, they track lineage and sponsor shows and things). The second link is the color and marking codes you may mark off on your registration papers (a long list, lol).
www.akc.org www.akc.org www.chihuahuaclubofamerica.com
www.akc.org www.akc.org www.chihuahuaclubofamerica.com