You sure seem to be focusing on the residence aspect and avoiding the employer aspect. But, I'll play along.
You seem to be missing the point that the whistleblowers would ALWAYS be the illegal aliens turning in the employer/landlord at the first opportunity, who else would know sooner than them?
If you insist of focusing on the possibility that the illegal alien who dupes the landlord into renting him/her an apartment for the reward, doesn't immediately turn them in, fine. Add a $50,000 false accusation penalty. You're on a tangent to try to complicate what is inherently simple.
If you hire an illegal, that same illegal turns you in for the reward.
And did you actually ask how the government is going to find out if you are or aren't a citizen? How about the same fucking background check we go through for a firearm, purchase?