Yeah - messengering is not very glamorous at all...
another interesting read is The Immortal Class by Travis Hugh Culley

many of them do work until they are so sick or so hurt that they can't do it anymore

Most alleycat races are not attended by a bunch of yuppie wanna be fixie riders. Most are put on and raced by messengers for a bit of extra cash, lots of free alcohol and a the rush....