Foreign Investment Tax in Victoria

I am a Kiwi with a son living in Melbourne. He has been living and working in Melbourne for 10 years and has purchased one investment property about 5-6 years ago. He is now contemplating purchasing another but we wonder whether he would be considered an overseas investor because he is not an Australian Citizen. When he purchased his first property it was as a personal home and he qualified for and received the first home grant; this property subsequently became an investment property. We would like to know whether we have a short time frame or a longer one to find his next property.