We had a 3 month notice period on our rental. We waited until we signed all the documents with the transfer/bond attorneys before we gave notice. At the end of this month, we have to move out. Since we have lodged already we are hoping to be registered by end of next week for the latest (cutting it super close). We had no delays with our seller, they were super fast submitting everything.
That said we did have to wait for the deeds office closures over festive. But also be aware that the deeds office can close at any time if there is a COVID outbreak which can cause delays. As
@newby_investor also mentioned, seller can drag their feet with certificates (which happened the first time I bought years ago. Whole process took 6 months).