Can i legally own a joey as a pet

Hopefully not. Some animals shouldn't be pets but working for a wild life sanctuary would be the next best thing.

you can work for animal rescue and have a house full of em if you want.

but not as a pet.

No. All native Australian animals are protected.
The only way you could have them with you is to be a qualified, licensed wildlife rehabilitator or carer.

I dont think so

Tie me kangaroo down mate.

Hell no. You're not responsible enough.