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Good afternoon. I am sorry to hear about your health issues. It is important to be aware that if the lease was signed and a deposit paid and accepted, the lease would have legal effect and you would be expected to perform and comply with it. If you do not, then they could sue you for damages. In this case, since there is a lot of notice, they can look and try to find another comparable rental. If they do and it is more, they could try and go after you for the difference between what they were going to pay and what they have to pay now. Moreover, if they already made/booked another travel plans and can not get refunded, they could try and go after you for that as well. If they are unwilling to settle and walk away, then you do need to place them on notice, in writing, advising that they will not be able to rent the property so they can start looking and try and mitigate damages
Do you know if they had airline tickets booked or anything else prepaid?
I just wanted to follow up and see if you had any other questions or needed me to clarify something. I am here to help, so please let me know. Thanks!