My father is 76 years old and his only asset is his house which is valued at $350,000. If I was to purchase 50% of his house for $175,000 and my father paid me rent of $175 per week would I be able to claim this as an investment property for tax purposes.
In short yes. But if the $175pw is not market rent for half the house then you will not be able to negatively gear it. Note when calculating the market rent for the house you would take half the rent you would receive for the whole house then reduce it by say 9% because you don’t need an agent and say 10% because you have a good tenant and maybe a bit more because your father does maintenance.
The down side is then only half the house will be exempt from CGT by the main residence exemption, assuming you are exempting another house with your main residence exemption. If it continued in your father’s name until he died then his heirs would inherit it at market value at his date of death. This arrangement will start to accrue CGT on the property. If the intention is to give your father some spending money maybe a reverse mortgage is worth considering. You need to crunch the numbers the tax benefits of negative gearing and possibly rental assistance vs exposing it to CGT.