Carlos, Jon, Steve, and Joel, you all make great points. And I think the idea of having Dec, but more likely Jan as the free month being a great idea. I'd rather pick Jan since that's the month I know they would fall behind (Christmas and New Years). I can even advertise that as my gift to them. And/or if I felt I should or need to, I could adjust the rent upwards.
These units rent easily at $400/mo and can rent for $450, so making it $433 to factor in that free month would be very reasonable. Although I'd be surprised if it wasn't so obvious that $33 X 12 = $396.
I dislike being underhanded, sly, or in any way appear dishonest. That's not in my nature and I'd like to pride myself on integrity. It would be nice to have residents who fulfill their obligation, but at the same time, at least I can try to implement other means in which a resident might be able to save money or be able to pay rent in a more convenient way.