In most cases, signing a lease obligates you to move in and occupy an apartment for the entire lease term. If you rented without thinking things through, you might want to cancel your lease before you move in. However, you cannot legally terminate your lease unless your landlord agrees in writing or the apartment is unlivable, regardless of whether you've moved in. If you terminate your lease early, you are still responsible for paying the rent until the landlord finds a new tenant.
A lease is a legal document; thus, once you sign your lease you are obligated to follow its terms for the lease period. It doesn't matter if you moved in or not; it only matters whether you signed the lease. State laws vary regarding breaking leases, although in most states you are still legally responsible for the rent until the landlord finds another tenant to take your place.
If you change your mind after signing a lease, contact the landlord as soon as possible and explain the situation. The landlord may be willing to terminate your lease, especially since you have yet to move in, and may not even charge you a lease termination fee. If your landlord agrees to terminate the lease, get the agreement in writing so that you will have no further legal obligation to him.
Find New Tenant
If the landlord finds a new tenant to occupy the unit, your legal obligation to pay rent ends. Thus, if you decide not to take an apartment after signing a lease and your landlord won't terminate the lease, you should help her find a new tenant so that you can be rid of the obligation to pay rent on an apartment you are not using. You can advertise in local papers or online, or refer people you know to the landlord.
In most states, you can break a lease if the environment is hazardous and the landlord does not fix it. For example, if you find broken windows or other hazards on your move-in inspection and the landlord does not repair them, you can legally terminate the lease. You must give the landlord a list of needed repairs in writing and give him a reasonable period of time to repair them before going to court to request lease termination.