<p>How are you doing in your courses this semester? How comfortable were you with the material before class started? It depends on a lot of different factors.</p>
<p>Have you tried asking other students on campus how much work to expect from those classes? Course numbers don’t tell us much on here, if MATH 101 is calculus it’ll be a lot more work than if it’s algebra, etc. Courses with labs tend to be more time consuming than non-labs.</p>
<p>Personally, I’ve had 20 units and been fine, I’ve had 16 and felt overwhelmed. It depends a lot on the school, the instructors, and you personally.</p>
<p>On not passing: Most schools have a couple weeks where you can drop classes after they’ve started. If you do try to do 18, just make sure you know when the drop date is, so you can get out of a class or two if it is too much.</p>
<p>Have you read the reviews for the professors you’ll be having? If they’re all “easy,” then you shouldn’t have a problem with the workload. If, however, you end up with teachers that give tons of work and have insanely hard tests, you may end up not doing as well as you’d like.</p>