Turning G3 ponies into G4 ponies, advice?

[aurastarlucario.livejournal.com]

Okay, so I was shopping with my mom and found an older My Little Pony book
with older characters in it.
I thought it would be pretty cool to draw some of the characters as FiM ponies! :3


But if I charge small amounts of money(no more than $1, probably) to allow people to pick
a character and choose whether they're drawn anthro or not, or an outfit for the pony
to wear, is that bad?
Copyright wise? What about by artists' morals? Would it be better if I did this for free?
I didn't think of it as a problem at first, but these are copyrighted characters...
So what do I do? :c