Start of a million questions from Australia

Buy back? Probably not. But there is no reason you could not simply put it on consignment with a dealer. Once you decide on a brand ot truck and trailer and have chosen a dealer i would try and make a deal,with them to buy and sell it for you at the end of your stay. As an option, you could find a place to park them for several months to use on a further trip. Or how about putting it into a rental pool and advertise it for rent lease to fellow countrymen? I know we get several a lot of Aussies asking about doing exactly what you want to do. Might make a decent way to either resell or rent it for weeks at a time.