Most of us have waited a long time to get the yorkie of our dreams. I am exceptionally lucky and received my little Izzie as a Valentine's present. I've been waiting for her for 4 years!!!
I've read your other posts... I could not imagine taking care of Izzie as a high school graduate/college freshman. I'm still in college, but I have an AWESOME best friend/roommate who helps me take care of Izzie. So far, her vet bills have been $150 and I've only had her for 2 weeks. I don't even want to think about how much money I've spent on all of her toys/bedding/food/piddle pads... I'm flying back home (California) for Easter. I'm taking Izzie with me. That's another $200.
I hope that you do what's right for you. I just want to prepare you, like others have for the expenses. Sometimes it seems that the puppy itself is the least expensive thing...
At the same time, please know that your life at 17/18 is going to be completely different than at 23. I would know!!!