Is the new owner going to allow pets? If so, then they would have to notify every resident about their pet policy. Have a pet policy in place stating the particulars about this policy. If not, they would need to notify the resident's of the No Pet Policy. Give the resident that has the dog 15 days to comply with the new Pet Policy, if they have not done so after the 15 day notice, then a 30 days notice would be given.