I am a Canadian flying to Hong Kong to visit as a tourist

I will fly one way. I don't know what other countries I will be flying to (maybe, Australia) or exactly when and intend on buying my flights while in HK When I land how do I provide proof that I will be staying for a few months and then will be leaving to go to another country without having an actual plane ticket? What can I show to prove I have money to travel and leave to fly out.