Do I need a co-signer to take out a loan?

At 18 years old you are legally able to buy a car and take out a loan without a cosigner, but I'm uming you tried this and the place said your credit wasn't good enough, or something. If this is the case I'd suggest just saving up your money as best you can and get an older junker, cheap when you are able. There are some older cars still in good shape. You can also try down the road to get a loan if you can up your credit/ income - maybe then the car place will give you the loan.