The way I see it, once we set this up the teams have to earn their way into the higher leagues. But it's not mandatory.
joe is a good example. He won the Pigeon Cup last season and a good sum on money. He chose not to re-invest and play in the $25 league this season. That's his choice. If someone else felt the same, I'd probably just offer promotion to the next in line in the standings. Moreover, if someone didn't get relegated and wanted to move down a notch, they can do that.
This is the only season you can just buy into the top league (so take advantage). After this season, you'll have to play your way in from a lower league.
The real question, and I'm happy to hear opinions on this: if you earn your way to the top and don't want to play. Can you sell your spot to someone else?