I live in NJ and need to break my lease, which would end on Dec. 14, 2014. I know in NJ the Landlord has an obligation to mitigate the damages by attempting to rerent the property but what if the Landlord decides they do not want to rerent the property they want to sell it??? It takes a lot longer to find a buyer rather than a renter.

In fact, before learning of her intentions to sell, I advertised the property and found a new tenant, same credentials as myself credit and income wise, who was willing to sign a lease that day and move-in August 8th paying $50 more per month than what I pay per my lease. The Landlord turned it down telling me her intention to sell and not rerent and that she was already under a listing agreement with FoxRoach. The Landlord offered to end my lease Oct. 31th if Iallow a lockbox, showings, open houses etc.

Do I have any recourse here? I hate to be stuck paying rent for August – Oct. when technically I had done my due diligence and found a new tenant.

I thank you for any information you can give me.

Not a lot. You are breaking a lease you signed willingly. If the landlord decides they want to sell, that is up to them. If you had an inkling you might need to break you should have tried to negotiate an early termination clause.

Does your lease permit a sublet?

'Due diligence' doesn't mean finding a new tenant, nor is it even applicable. A landlord is under no obligation to like the person you found. You don't really have any recourse, but I would negotiate. I'll bet that you can get one more month off. There are 'nice' ways to imply that you will be more amenable to showings and will keep the place clean and neat.
(PS: Lockbox? NO! Not when there is a tenant in the house! She is very naïve, I think. If she wants a lockbox, then that means you are totally moved out, and not paying a dime. In fact, each state has laws about reasonable showing of a rented property, and you could make it easy for her, or hard.)

They do have an obligation to attempt to rent the property.

If they do not, attempt to rent the property, that would be a defense against owing them any future rent for breaking the lease.

But it will be up to the judge and you will have to show proof, evidence in court, that they are not attempting to rent.