To decide if it's a scam or not, do the math.
Using simple numbers, if you pay $1000/month for rent today, and nothing changes, it will cost you $13000 for 13 months.
If your landlord offers you 13 months for only $12000, you're basically paying nothing in that final, 13th, month. You get locked into the lease for an extra month, depending on the specific terms of the lease.
As long as the terms of the lease are expressed clearly, you can easily compute your savings, the timing of said savings, and your other obligations under the lease.
Not sure how that's a scam. Might not be what you want, and that's fine. But not being what you want doesn't automatically mean it's a scam.