Under New Jersey law, you as a landlord with a month to month tenant can terminate your tenants lease with a month's notice. Simply write them a letter.
I am not your attorney, I do not represent you. This response is submitted for informational purposes only. This is not legal advice, nor is it intended to be taken as such. Anyone considering the above referenced situation should always consult an attorney within the jurisdiction before taking any action based on this, or any other information.
Unless the building is opwner occupied with not more than two other rental units, you can only evict a tenant for cause as defined in the NJ anti-eviction act. For example, if the property is a two or three family and you live in one of the apartments, you can give one month's notice before the beginning of the term (e.g. the first of the month) to vacate prior to the first of the next month. If not, the notice requirements vary depending upon the specific cause for eviction. However, you shopuld contact an experienced NJ landlord/tenant attorney.