It's not that unusual to still be living at home well into your twenties now days. If you wish to own a house early on in life it's almost a necessary step. Share houses too. While it could be possibly renting, such as renting a relatively cheap apartment or a small house in the outer suburbs for a couple years, it does require frugal living. Let's say you are paying $310 a week in rent for a small city apartment, that's $16,000 a year, if you spent $70 on groceries a week, that's $4,200 a year, commuted via public transport, you can probably scrape by with spending $25,000~ a year (considering bills, you may have a car which needs servicing, so on).

No idea what their job is, but let's say they've been in a properly paying position for three years (may have done apprentice ship, uni, whatever) and earn $75,000 a year, that's $225,000 - $300,000 total over the probably 3-4 years they've been working. Subtract $75,000 - $100,000, you get a potential of $150,000 - $200,000. If you spent a third of that on things you want (not very frugal, but just an example) you still have ample money for a deposit.

The hard part is usually getting a bank to secure a loan for you when you are young, often a guarantor is needed for that.