Prostitution will never go away. Always in demand, always will be, However, that does not mean that an individual prostitute has a stable job. If Leroy gets sent to the big house, Streetwalker Sally is effectively unemployed, unless she wants to go freelance, which has it’s own risks. Drug dealers are the same way; if their supplier stops supplying, they need to find another gig.
In current-day America, I think that many jobs in the financial sector are pretty stable. If you do your job wrong and lose money, you lose someone elses money, and unlike drug dealers and hookers, you are effectively immune from prosecution.
Most government jobs are not as stable as you think. I know too many ex-government employees that went into involuntary retirement or just plain got laid off to think otherwise.
Police officer is one of the few government jobs that is secure since there are plenty of bad guys out there, and not enough people to catch them.
Lastly, there are job-seekers. Sure, they can’t pay the bills, but in this economy it’s a pretty stable position; those without jobs are going to be without them for a while.