>Why isn’t a year upfront incentive though?

For one thing its actually illegal

Landlord tenant law is chock full of things that the parties are prohibited from agreeing to do.

Sure, you think you are "volunteering" to pre-pay (so it's not the landlord "requiring") but if you can volunteer, why wouldn't a landlord refuse anyone who did not also volunteer that?

The law strictly limits what a landlord can accept in advance, because what they can accept is in practice what they can require.

It's indicative of someone with cash flow problems. Once they move in, it's really hard to get them out. What happens when the lease is up and the OP can't/won't pay? Evicting someone takes forever.

It could also be indicative of somebody who obtains the money illegally. Technically if it doesn’t go into a bank and goes into an apartment it’s sort of a way to launder the money.