how do i get started selling personalized Disney books?...?

Answer 1

Get a hold of Disney and request licencing rights before you do anything. They are known to protect their trademark agressivly.

Answer 2

most likely you'll have to have a business license,for sure you'll have to have a state tax number,then whether you are selling on the web,out of your home,or in a shop somewhere you'll need to contact Disney the division that handles there official licensed products,in fact you may need to acquire a special license from Disney-though unlikely.
Or perhaps simply after you've acquired your tax number etc you contact a few book wholesalers.