If my son was 26 and still at home, I don't think it is a bad thing. After all nowadays, this is a normal appearance and many people will agree with me.
Firstly, maybe the young man isn't married, he is studying, working. Living at home, I can look after him better, and he also can be absorbed in his working, studying. He can get good progress. Above all, in one's all life, the choice of career is one of the best important things, so I think every parents should help their children, when they are in this period.
Secondly, the rent or the price of flat is very expensive in Syndey, in addition the costs of living also spend a lot of money, to a single man, it's not necessary to spend it. Even if he is married, if it's difficult to him to afford these all costs, and my house is large enough , I still think his family can live with us, of course, he's better to afford a part of living costs, this is his responsibility.
Thirdly, nowadays, a lot of young man like to be single, they try to court a kind of free life, so if he lives with his parents, he enjoys his family life which is harmonious and happy, at the same time the activity of his parents affect him, so the marriage follow as a matter of course.
For all these reasons. I think a mature young man lives with his parent is a normal appearance.