Disorient,
Before you decide on a Yorkie there a couple of things you need to know. *Some* Yorkies can be difficult to housebreak. *Some* Yorkies (probably a majority, even) can be yappers - ie they love to bark. If these are things that your mom won't not be able to tolerate, you might want to consider another breed or wait until you are on your own. Save yourself the heartache of having to rehome a dog that you love!
If you are going to get a dog - any dog - I highly recommend that you spend time reading on this website:
http://www.clickersolutions.com/arti....htm#behaviors