The ATO will consider your intention – if your intention is to buy and sell for profit then the time period that you hold it for is irrelevant – you are in business and you will not qualify for the CGT discount. This will particularly apply if you do a lot of renos. The CGT discount only applies to investments.

I don’t believe that there is a “min time period” of living in the property that means that there is no tax to pay on it.