While co-signers with positive credit can help improve your financing terms, they certainly aren't required. Co-signers are used when there isn't significant proof of gross monthly income, proof of residence, a valid driver's license, proof of full coverage insurance, six personal references, and rent or mortgage is not current. In addition, if your total debt, including rent or mortgage, along with any debt listed on your credit bureau report, exceeds 50% of your verifiable gross monthly income, or you have an open automobile that you are not trading, you may be required to have a cosigner to budget for additional debt.