If you have been asked to co-sign a loan --- for anything at all --- there is a little bit of math you MUST understand before you sign anything:
1) co-signer =
2) borrower =
fully responsible for paying back loan
3) lender =
(creditor who could not care less that you did not understand that co-signer = borrower)
If you do not understand what those three identities are telling you, PLEASE do not co-sign a loan for anyone or anything without consulting an attorney first.