When we came back to Australia we had to give our tenants 60 days notice, because they were on a periodic lease (had not signed another 12 month lease after the original period) and the notice we had to give them was dictated by the tenancy board of Victoria. They could have left the lease with 2 weeks notice to us, but we had to give them more. It would have been even longer if we had not wanted to move back in ourselves. Your state's tenancy board will be able to tell you how much notice you will get.

As for moving from a large house to a small one, I have done it and it is not fantastic fun, but in the short term it is definitely do-able. Consider hiring a storage unit for your excess furniture and it will make the unit much more comfortable.