Are you taking on the entire lease yourself and then hoping to find a roommate? Even if your credit is great if your income isn’t enough to cover the rent without eating up about 50% of your net income then that is why they are asking. If your income can’t pay the entire rent then asking for a guarantor is a reasonable thing. If you can find a roommate and then both of you are on the lease then it shouldn’t be a problem. Your LL may also be use to renting to students and automatically assume a guarantor is needed. Talk to LL on why they need this and that could solve the problem.