SOLVED. Old Sci Fi story where young adults can do what they want, at age 30 assigned job where you pay off the debt incurred as youth.

[Sandra]

There was this story I read when I was quite young, pretty sure it was a
short, where in the contemporary society you could do anything you
wanted as a young adult.

You were basically accruing debt that you would have to pay off by
working. Once you hit a certain age (30?) you were assigned a job to
pay off those debts. The more you owed, the harder the job.

While many people were careful not to accrue too much debt, the
protagonist of the story lived the party life and cared not what he spent.

On his 30th birthday he tried to cheat the system by jumping off a bridge.

He then woke up with his brain implanted in a ship and a debt that was
going to take hundreds of years to pay off.

This story could have been a precursor to the later "Brain Ship" stories
by McCaffrey, Niven and others.

[Ayshe]

It looks resolved on scifi.stackexchange: Wasted on the Young by John Brunner.