How often do new leagues start, I would like to start a franchise from the start.

Too many older worlds with openings, doubt they would start a fresh one

I don’t think there has been a truly new world in at least 15 years, maybe more. When a new world pops up, it’s because two (or more) previously existing worlds fell apart and were unable to fill a huge number of openings. They take the teams from the worlds and mash them together to form a new one. I don’t think it’s incredibly easy to join one of these, unless you happen to be in one of the collapsing worlds and keep your team.