[hiAndrewQuinn]

Realistically, it was probably graduating high school. It's step one in the so-called 'success sequence' for a reason:

1. Finish high school.

2. Get a full-time job once you finish school.

3. Get married before you have children.

97% of millennials who followed that sequence avoided poverty by the time we hit age 30 or so, so it's got a pretty good success rate. #2 has the most immediate impact here, but #1 makes #2 much easier, and not following #3 sadly makes #2 moderately harder (juggling childcare is tough even in the best of circumstances).

Finishing college would be a somewhat distant second, as it makes the entry pathway into a lot of white collar jobs a lot easier, even internationally. This was especially important when I realized pretty soon after finishing college that I had good reason to leave the US.

I'm now happily married with kids and full time employed in a senior position here in Finland, all by 30, so I'd say I've done pretty well for myself.