There was a advertisment for a professional hermit a couple of months back in Britan. Cant do better than that.
[hijack]
How does one become a “hit” man anyway? Is it one of those jobs where you had to know someone who was on the “inside”? Or could you just roam around around until you found a person likely in need of your services? (I.e., divorce, bad partnership, etc)
Not that I’m in the market, but with this economy you can never tell. 
I think you’d advertise. All you need is a catchphrase and a gun. Try an old standby…
“Dirty deeds… done dirt cheap!”
Forensic examiner. Not necessarily people who cut open dead bodies but people who look for physical evidences at crime scenes.
Professional game player.
Let’s discuss your rates, my ex-wife, etc., etc.
I agree with Sam Stone. Say no more.
OTR truck driver.
Some make great pay, especially if you’re hauling explosives, toxics or radioactives.
Some routes you spend virtually all day alone in the cab.
Ummmm, did you happen to miss the last 2 years? Besides, even mud-phuds have to scrounge for their income these days. Ever write a grant proposal? shudder
Most writers do a lot of PR work and go on the road doing promotion. It’s not a particularly solitary way of life any more… The actual writing is but what goes with it involves a lot of people contact.
Radiologist, pathologist, accountant, tax lawyer.