In NJ real estate, what is common practice for timing between closing

Usually when the closing occurs, the new owner takes immediate possession.  there are often reasons why the seller cannot move out immediately, and then he attorneys involved draft a use and occupancy agreement that sets forth the terms of how long, and at what cost, the seller can remain.  Once the closing occurs, it is the buyer's property and the seller has to vacate if there is no Use and Occupancy Agreement in place.