There are plenty of people who either work full time or are in school full time while studying for their MCAT. In is certainly possible to do for your average student that ends up matriculating. However, that is completely irrelevant. Just because someone else can, doesn't mean that you can or should. Doing well on the MCAT is incredibly important for getting into medical school and having a choice of school to attend. You need to do what you need to in order to maximize your chances of doing well.
That having been said, if you can't handle a minimal course load or a part-time job while studying for the MCAT, there is something wrong. This is not meant to be disparaging. This is meant as a heads up. You need to get more efficient. You need to get more organized. You need to learn how to learn. And, most importantly, learn it now before medical school/residency.