Two levels of CA can be pursued along with job. But in that case, job will be distracting factor in your studies. However, if you feel that you have a caliber to cope up with your job and CA, then you can definitely go for both. After clearing your first two stages, you will have to join a CA for 3 years compulsory articleship. Therefore, at the CA final level, you will have to quit your job to fulfill the training requirement.