This is probably common sense and not sure if its an exploit or guide but I wanted to see if I moved a character from my wifes battlenet account to mine would that character bring all of the mounts with it. Well I grabbed a level 20 alt she had that had all the mounts and pets and moved it from her account to mine (same last names) and it worked.
I now had all of her mounts on my battlenet account. I went from 4 to 103 mounts. It seemed the pets did not however come across.
I find this a little op in that some mounts out there people would pay a mint for if you were to sell accounts with a ton of mounts attached.
Sorry if this has been posted, I figured if you wanted to know if it worked without spending money first Id let you know my results.