When do gypsies (travellers) settle down?

Have been watching the Big Fat Gypsy Wedding on TV here in the US. I am wondering when a traveller decides to settle down and buy a house. I see that some of the girls' parents have homes and when the daughters marry they start the life of a traveller. Why do they do this? Are adults still considered gypsies when they own houses? Is it required to "do your time" as a traveller before settling down? Please feel free to go into as much detail as possible.