I have a friend who has a great deal on their current apartment with a large rental company, but will be moving in March.

I'd love to take over their lease, but from the information I'm finding it looks like the landlord can decline any unreasonable request for a lease assignment. What constitutes unreasonable?

Beyond that, I also have a great deal on rent, and was hoping to pass my lease onto some friends, in the weirdest game of millennial musical chairs.

What issues might we encounter while trying to assign a lease that is under market rate? How can I increase my chances of success? What should I know about as we pursue this? What is the correct procedure to follow to make this happen?

Apologies if there's an existing thread somewhere; I looked around, but most were people looking to assign their lease, not looking to take over someone else's.