Usage patterns
〈人〉の保証人になるto become someone's guarantor
He became the guarantor for his friend who was renting an apartment.
保証人を立てるto provide/arrange a guarantor
To take out a loan, you need to provide a guarantor.
〈人〉に保証人を頼むto ask someone to be one's guarantor
I asked my father to be my guarantor.
保証人が必要だa guarantor is required
A guarantor is required to rent this apartment.