If you do not know what you are doing, yes, they are hard to potty train. Baby was my first Yorkie and she STILL has "accidents" on the floor. She is 2 years old. If/when I get another pup things will be a lot different the second time around. Good luck!
Oh, and if you are having doubts about the "breeder" (who doesn't sound like the actual breeder) get out now why you can and find another pup...Yorkie or not!
Stick with your gut.