You don’t need to quit working or take time off for your GMAT. 12-14 weeks, starting with around 15 hrs/wk (~2 hrs a day) and then ramping up to about 25 hrs/wk, is generally what it takes to go from “oh man! I had forgotten my basic math and comprehension” to being competitive at the exam.
The GMAT concepts are relatively basic, but they require a deep understanding to tackle nuanced questions effectively. So lets dumb it down for us. This is not just a math and English test—it is a deductive test designed to assess your problem-solving skills. Without thorough knowledge and the ability to apply it, the test can easily trip you up.
PS: No, I don’t do "in-exam help" or "exam-proxies". If you can’t handle the GMAT honestly, how will you manage an MBA? Face it straight or don’t bother.