Generally, natural persons who require banks to provide loan guarantees all require a fixed job, a fixed income and a fixed residence. What your friend wants to sign is a loan guarantee that belongs to joint liability. In other words, when your friend is unable to repay or doesn't want to repay at all, the bank will recover the remaining unpaid money (including principal and interest) from your guarantor. Simply put, if your friend doesn't pay back (no matter how much money is left), the bank will ask your guarantor to pay back together.