If you break your lease six months before it ends and if the landlord makes no effort to look for new tenants can he sue you for lost rent?

It has been my experience, that if you break your lease prior to expiration of the lease term, you are in breach of contract. In NYC, unless you obtain signed and written consent from the landlord granting you permission to end the lease prematurely, he can sue for lost rent. I had a verbal agreement to end the lease early with the landlord of my first apartment in the city. I was in the process of moving out and he padlocked the premises with some of my belongings inside, and then sued me for back rent 6 months later and won. (Although I never paid based on principle. He had given me his Word and then renegged. I made a naive mistake and he took advantage of me.) Never do anything with out the other party signing an explicit agreement.

Many landlords, if given a month or so notice, will waive the requirement, but it is at their convenience. If you are going into the military and you have the correct papers, the lease can be broken.