Stairs shouldn't be an immediate issue if she lives in an apt and they take an elevator to the floor. However, there are stairs everywhere an she may need to be taught how to use them. There's always the carrying method....
Also, as the Yorkie gets older, you may want to get small stairs so that the Yorkie can get up and down from furniture (if she's allowed there).
I had to teach both of my greyhounds to go up and down stairs because carrying was not an option (not at 62 and 77 lbs, respectively). Anyway, I think it's a little scarier for older dogs, than puppies. Puppies are more daring (almost said nutcases
).