This is a simple scam that can be done several ways.
1) buy cats from the cat vendor in elwynn forest (32s)
-i choose bombay...sells well for me
2)Resale in trade for 1-10g np
you can also try auction house but i never have tried.
it may look good compared to the 50g white kitten
this can also be done with the rabbits sold in dwarf area or owls in darnassus, but i have never tried with those