Pavisai

Hi All, My parents are here with me in Perth,WA in visitor visa subclass600. They came here in 2020 Feb and we have extended the visa once already for a year. Now again their visa is going to expire in Jan 2022. My father is 70 years and my mother is 60 years old and I am their only daughter. I am looking at options to bring them here with me long term or permanently, which ever is possible and affordable. My dad is a liver cirrhosis patient and is well compensated and manageable. He is not ill or anything. I am worried which visa would be the best option to go about. I can see only my dad is eligible for Aged Parent Visa 804 and not my mom. I am not sure if my mom is eligible for any visa that would grant bridging visa. I am very confused now , I have an appointment with an immigration agent this week but still looking at any advise that would be helpful. Can my mum be included as a second applicant in aged parent visa 804? What are the feasible options to extend their stay for now ( if nothing else suit them ) ?