This is a very interesting and illuminating topic. If we are interested in prediction and prevention (and some of us are), it's great to explore.
It's possible Bryer didn't actually graduate. However, somehow, I doubt that Grandma would have had major consequences for him, for that. Perhaps both boys were being pushed in the direction of employment (as I posted earlier, many families do in fact find ways of "making" their kids launch, sooner or later). Kam was out of high school for what, a year? With no employment? Lots of parents would be annoyed, especially if all the time was spent playing games and none of the time was spent running the household. An adult child living in a house without contributing income should (in the views of many) being taking on virtually all the housework. Just saying.
I can surely imagine a scenario in which getting "kicked out" of the house meant "Here, you can have this truck and camper." Because that's what I see in my own neighborhood. Middle class/working class people. More than once when my daughters were in high school, they asked if a friend could pitch a tent in the backyard (nope) or park their car or van alongside our house (two nights only - that's what the local ordinance says and really, no one is supposed to sleep inside).
Just a month ago, on nextdoor, a neighbor reported that a young adult had set up a tent in their backyard, in an area behind a couple of trees. They figured he'd been there for a while and they hadn't noticed. They took it down and tossed it over the fence (they were not pleased), along with a yoga mat and a sleeping bag. They live not far from a park where restrooms open at 8 am. So yeah, some kids get kicked out and try camping.
The amount of high stress interaction that occurs right before the kid is finally "kicked out" can be major. It sometimes results in complete rifts between parents and offspring that last for years - or forever.