I go to school full-time, and work full-time, and take care of my yorkie full-time. Sound easy? It ain't!
Though it can be done, the question is... is it fair to your yorkie? I keep mine over at my parents when I'm at school/work so he can play with my parents dog. Would I have to keep him home alone all day by himself, I would have felt horrible and not have gotten a yorkie. It wouldn't have been fair to him.
If you're just lonely and need a friend, I'd invest in a fish. If you have the time, and patience, to TRULY take care of a little guy, then by all means, do it. If you can't, then do the dogs out there a favor and don't adopt them.
I'm sorry to sound blunt, but this hits close to home. Kingston's previous owner kept him locked in the pantry from 8 a.m. to 6 p.m. every day while she went to work. I can't tell you how upset it makes me to think of how lonely he must of been and how I see how her behavior affected him on a day to day basis. I have to "re-train" him on multiple things... for instance, he thinks it's acceptable to pee on himself (which is against dog's natures) because she would lock him inside without a place to go to the bathroom. She was "lonely" and thought she needed a buddy to help her make the transition. To me, that's selfishness, not love.
Only you can answer this question honestly. Can YOU afford the time to take care of a dog while going to school? If you can't, then you should wait until you graduate... keep it as a "graduation present" for yourself
Best of luck in your decision,
A 21 year old college student