If you signed a lease that does not end for 15 months, you are legally responsible for completing the lease term. If there are extenuating circumstances, you should talk to the owner/manager who *may* allow you to terminate early (with a penalty). Our state law is that the landlord/manager must do their "best effort" to find a replacement tentant. But, legally you would still be responsible for covering the remainder of your lease term (even if it did actually take 15 months to find a new tenant). I wonder how you can enter into a legal contract then just decide "oh, nevermind, I don't want to do this anymore" and leave someone else on the hook?! As a landlord, I have a lot of flexibility and compassion for my tenants and will help them out when & how I can, but trying to back out of a lease FIFTEEN MONTHS early?! Anyways, sorry for the rant, but we've had 2 tenants who just decided to up-and-leave early in their leases... and left us scrounging to find new tenants!
If, after 3 months, there haven't been any applications, the rent is probably too high for the market. Of course, you can just bail on the property, but I would suggest talking to the landlord to see if they can work with you (maybe reduce your rent for the remainder of your lease)? Otherwise, you could be taken to court and sued. You might want to think about your circumstances before you sign another lease...