I'm 18 and own my very own yorkie baby. I am a full-time university student, I work two part time jobs (45+ hours a week total), and I have a "healthy" social life. I can take Wobie with me to one of my jobs, most of my classes, and every social event I go to. So he doesn't get left alone more than a few hours a day. Sad to say, but I would not have brought him into my life if I couldn't devote enough time and energy to giving him the best life I could.
Its hard to balance it all sometimes, but so worth it.
Trust me, it will get harder when you have to handle all the bills by yourself, and have no one to watch your baby when you're at work or school, and fit in times for walks and stuff in between everything else you have to do. But as long as you love your baby and are committed to his well-being, you'll get through it.
