I think you said it, galain.
I don't think they make enough money to live off. Although I am CERTAIN that some of them have made at least a million or two...and they should be able to invest that. Even invested in a GIC at 2.75%, $2M would yield $55,000 per year.
Why more don't do THAT...I don't know.
And those are only the top ones. The ones outside the top 10 need to work jobs even while competing in their primes. So...I have no idea what happens to them.
Presumably, they work as personal trainers or in other similar capacities, or sell supplements or steroids, to make ends meet.
But your guess is as good as anyone's.