Be nice and include a clause in the lease that allows them to terminate the lease contingent on them closing on another commercial property and with no less than 60 days notice.

ie tenant is responsible for checking the smoke detector battery every six months..

Yes, if you fail to terminate properly you can go into a month to month which may require a different notice requirement.

My other reason was battery life.

Investing long term in real estate is like finding a good women.  

As a wholesaler you have a contract with the seller and so you have an equitable interest (I think that's the correct term) in the property, which allows you to market the property to buyers.  

Hi Lars,We have been doing short term in Los Angeles since October for similar family reasons.

His 6 month lease was terminating on the 31st and he wanted to know if he could hold over on the weekly bases. when I questioned it he countered with  "or do the month" later he informed me he would pay April. 

Is there any legal restrictions in putting an early termination fee in a lease for the state of NJ?  

(Terminal caps and gel available at Home Depot or Lowe's.