The Teacup Chihuahua is not a separate breed, nor even a breed. She is simply a miniature Chihuahua. She is a dog like any other, who needs a dedicated owner.
As we have seen, we're talking about a dog with specific needs due to her special size. She does better with a single owner in a household without children and without other pets who aren't Chihuahuas.
It's important to look for a reputable breeder, and to bear in mind that, if buying her as a puppy, it is impossible to know what size she will be as an adult.
A Chihuahua, teacup sized or standard, is a long-term commitment and you should consider it seriously before starting this adventure.