It can be done, much easier these days. A friend of mine did it may years ago when she was 21. She hadn't planned it, but someone she worked with had planned for a 1 year working holiday, but due to family matters couldn't go at the last moment. She was offered the ticket and visa and without a lot of thought, accepted on the spot. They managed to get it all transferred into her name and 2 weeks later she landed in Sydney on Australia Day 1988, the day we celebrated our Bicentennial. She knew little about Australia and walked out of Sydney Airport wondering were do I go now, so she jumped in a cab and said, "take me to the Sydney Opera House". That day the Opera House, Harbour Bridge and Sydney harbour was the focus of the Australia Day celebrations with the harbour filled with boats and foreshores lined with huge crowds to celebrate all day and night. Tall ships on the harbour, fly overs, entertainment and topped of with the biggest fireworks on the harbour ever. It didn't take her too long to realise it wasn't just a normal day, she had just been lucky enough land in from London for our 200th Birthday Party.
She didn't have much money as the trip was basically unplanned, hadn't saved up to travel, but had been working in 6 Star Boutique Hotels, trained as a chef under some of the UK's best chefs at the time, so finding work wasn't hard for her. Her plan was, get a job work flat out for a month or two, then use that money to travel and tour the country. When money got low again she'd work for another month then move on again. The "back packer" trail is now well established and air travel so much cheaper these days compared with her saving the money and hitch hiking with long distant truck drivers in all directions across the country. She did this for the year and did cover the whole country before she returned to England. A year to the day she landed back in Sydney, on Australia Day 1990 this time to stay
Hope your son enjoys his trip, and don't be surprised if he wants to come back here after. I have a co-worker that moved his family from Ireland about 18 months ago and has gone from strength to strength since. My Grandparents came over in 1949, to escape the London smogs as my Grandfather had a bronchial condition, and was told by his doctors to emigrate and live or stay and die in London. My parents and 2 sisters' followed 10 years later as 10 Pound Poms in 1959, with me coming along in 1961, Aussie, Aussie, Aussie.