Ruling 2332
The person for whom an individual acts as guarantor must be in debt. Therefore, if a person wishes to acquire a loan from someone, one cannot act as guarantor for him until he acquires the loan. This condition does not apply to the second type of suretyship [mentioned in Ruling 2329].
-Ayatullah Sistani, Practical Laws of Islam, Suretyship (Ḍamān)