My question involves landlord-tenant law in the State of: New Jersey
My parents rented their apartment to a couple with two kids last year. They had some problems with the tenants from the beginning. The tenants had 7-8 neighborhood kids in and out of the apartment every day, and they had loud parties until 5:00 am. My parents spoke to them regarding the issues, but the tenants continued to do the things they do. A few months ago, the tenant couple had a huge fight, and the cops came and arrested the boyfriend. The boyfriend is still in jail, and the lady moved another guy with big dog into the apartment and didn't' tell my parents. Then, the lady and the new guy started doing drugs in the apartment. My parents had enough and decide to give them a 2 months noticed to move out. They were supposed to move out by the end of August, but they stayed for over a week. They finally moved their things out of the apartment on Monday. But, they didn't come back yet to hand over their key and get their safety deposit back. My parents want to know, how long should they wait before changing the locks?

