I have broken leases twice in my lifetime, once to buy a home and a second for a job related transfer. In both situations, I offered to post ads, show the home and assist in finding a new tenant. This on top of the regular cleaning and leaving the place in better shape than when you received it.
I am going to face this same scenario again in the coming months as I am going to buy at some point. I told my current landlord of two years plus at the time I reupped my lease that I would probably be leaving before the year was up and that I couldnt plan around a home purchase.
This isnt so much an answer for you as it is a solution for others that may read this in the same situation. If you are up front with the landlord, help find new tenants, and have a good relationship with the landlord from the start you should have no problem breaking the lease. It also helps if your current rent is low relative to the surround rentals. It will make filling it that much easier.
