When DD was 16, her boyfriend (15) and his sister (17) lived in a very high end condo, owned by their parents. The parents had built their dream home near a ski hill, 40km outside of the city, but wanted the kids to stay in their school, which was two blocks from the condo.
Totally selfish. And yes, the kids turned out badly.
Fortunately, DD is very tight with money and we had told her that if she could honestly tell us she hadn't smoked tobacco by the time she was 16, we would give her $1000. BF decided a girlfriend who wouldn't do drugs with him was boring, so the relationship was over after a few months.
DD put the money into her university savings account.
I actually think one reason they got away with effectively abandoning the kids was that it was an expensive building and the neighbours didn't pay much attention to each other. Social workers don't often get involved with rich families.