Trust me, if you're in a bad roommate situation, get out of it immediately even if you have to leave the cheaptest coolest-looking apartment in the world. It can be done. No amount of money you might save is worth your peace of mind, human rights, and privacy.
If you honestly can't afford to live on your own, move out of that bad living situation now, find a new place and get better roommates. (Did I mention that Dec-Feb is the BEST time to find an apartment and roommates, just look at craigslist!)
Never agree to live with someone if you have the slightest bit of doubt about them or whether someone you like might not be compatible as a roommate. Always go to their current place and see how they live, that is a good indication of how they will be when they live with you. If you're stuck between a rock and a hard place and have no choice but to live with someone you have a bad feeling about... make sure you do NOT let them on the lease. It must remain your apartment and yours alone. If the roommate doesn't work out you must retain your right to ask them to leave. Do not let them guilt you into getting on the lease or letting them stay if things don't work out. They will never change. They will not chane. Trust me. Oh, did I mention that they will not change?!
REMEMBER: You have every right to choose who you live with!
You have ever right to have friends over. You have every right to live in a clean environment with someone who has the same values of cleanliness as you do. You have every right to live with someone who will clean up after themselves and do their fair share.
It's up to you to change your bad roommate situation. Never compromise your comfort level.
Sorry to sound so didactic and all that, but I know from very very unfortunate experience that living with someone you hate is the worse thing you can do to yourself.