It really depends on the community and what the agreement states. Some places allow the resident to avoid any penalty if he/she has to move out due to an illness or, worst case scenario, death. Good luck!
Have you tried going to the rental office and speaking with them directly. I have found that if you explain the situation most will accommodate. The next question is can you sublet to someone else or another family member.
I would assume that this varies with the state where the senior lives. I'd check with your Social Services people and see if they can point you to the right local people to ask, or else go to your state website and look for links. Type your question in the search box and you'll likely get some direction. Good luck, Carol
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Carol