I am a co signer on an apartment for someone with bad credit - if this person defaults?

...since you're a "co-signer" YOU would become the responsible person for the rent "if" the person you signed for defaults... usually, the Landlord will have the tenant evicted (with at least 30 days prior notice)... "If" you fail to pay the past due rent (etc.) "they" can sue your for the money owed... (Small Claims Court) get a Judgment against you that will "trash" your Credit Report until you get the past due money straightened out... If you know that you know that you know this is going to happen... try going to the Landlord and explain your situation to them, (people) are generally reasonable and will work with you... Good Luck...