Thank you so much for your reply.

My lease has an addendum attached which the old one doesn't. Based on the addendum, the tenants need to pay for certain repair undoubtedly (according to my PM and another experienced landlord, the tenants need to pay it as well even without the addendum). I mentioned it to one tenant (a college student) once and the tenant's roommate's father, who is an attorney, sent me an email saying he would sue me if I deduct their deposit. I did not intent to deduct their deposit because the tenant is a good kid, who works hard and is willing to move to a less expensive apt to save money instead of using parents' money, which I doubt my kid will do in the future. I simply donot like that attorney's tone, I just want him to know I am not scared by his treats if I do not deduct their deposit. So I 'd like to have some legal documents in hand showing I have the right to deduct their deposit but I won't.