Well, honestly, I'd wait a few months before doing either. Try to get all of your scores above 600 before applying for a car loan. With your scores right now, you'll probably get saddled with a yucky rate, like 12% or worse. Dealerships like to finance people above 600, and even more so, above 680.
Right now, I'd save the money each month you might put toward a car or an apartment and get yourself a very nice down payment. That makes the dealership happy and they can probably get you a better rate to finance.
Talk to your credit union also. Credit unions usually have better rates for auto loans than banks like Wachovia, but the best rates still apply to prime borrowers. You might get a 8 or 9% with your credit union, but your better off to just ask. Print out your reports and bring them in.
I applied for auto financing a few months ago: my scores a month ago were 640/657/670. I got approved for a 9.9% rate through the dealership. That was too high for me, so I got a few lates deleted with GW letters. My TU score went up 31 pts, so I'd assume the others went up also. Last week I got approved at 6.9% by myself with a 688 TU, but with a cosigner (FICO in the 800s) I qualified for a 2.9%.
Anyway, I'd work on getting everything about 600 first. Depending on which report they pull (and many pull all three) you'll probably fall into the "subprime" tier of borrowers.
And if you like your living situation, I'd stay there and buy the car first. At least with a vehicle, you have something of value at the end of the terms.
Good luck!
- Catz
12/01/09 TU 759 EQ 756
10/01/08 TU 697 EQ 659
07/05/08 TU 693 EQ 663 EX 711
06/01/08 TU 657 EQ 610 EX 670