Which doesn't narrow it down at all, as ALL Australian Visas are e-visas, plus what he is most likely referring to is an ETA which isn't really a visa at all...


For a US citizen there is no requirement for a return air ticket in order to enter Australia. That means that this falls to the normal requirements for entering Australia (and most any country) that the immigration officials must believe that you will meet the conditions of your entry, which includes being able to support yourself without working in Australia (presuming a non-work visa), and that you will depart the country before you allowed stay expires.

There's no exact rule as to what that means, but being able to show a credit card or two isn't going to hurt. Having a bank statement (or even just an internet banking printout) with you certainly isn't going to hurt (presuming it shows a reasonable balance obviously!), nor would any details showing residency elsewhere. None of that is necessary, and there's a real chance they won't even look at any of it, but it won't hurt to have it available "just in case".