Each trade you make with SIX will have a minimum flat brokerage fee of $9.90 on trades up to $9,000. Brokerage of 0.11% will apply to trades above $9,000. There are no join fees!
The minimum amount you can invest on the ASX (i.e. the smallest amount of shares you can buy) is $500 for the first transaction. This amount does not include fees so your first deposit will need to be a little more than $500. Once you hold shares in that company, there is no subsequent minimum.