I want to die before my mum and sister because I don’t want want to be left behind if they die first

I’ll have a roof over my head my sister said she’ll leave this house to me but how am I going to pay for the bills on my own I only pay $300 a week to my mum through my trustee who’s going to take care of me I know I’ll have carers from ndis so I guess I might be ok I don’t know