Q:

A man takes riskier and riskier jobs (involving a transportation ring) for more money

I'm looking for a story I read in 1980. It is a short story and may have been in one of Asimov's or Bradbury's collections.  
It was about a man looking for a job.  He goes into an office with, I believe, a help wanted sign on it. Inside is a beautiful woman and a robotic(?) filing cabinet.  
He is allowed to state what the risk he is willing to stake for the job.  The odds are his chances of coming back alive (1:1 = %50)  The woman is a secretary and she asks him what odds he would like.  He asks for one with a great chance of return, something like a 1000:1.  The filing cabinet spits out a listing and she gives him a vague description.  He takes the job.  She gives him a ring and says if you want to return just press the center of the ring and you'll be transported back immediately.  
So he arrives at his new job and instantly he is mobbed by the indigenous creatures giving him buckets of their money.  He didn't like it so he goes back and asks what it was all about, the secretary says he was collecting sin tax on an alien planet.  He didn't make much money because the odds were low risk. 
Another job he had I particularly liked: he was a mechanoid being eating every sample of vegetation he could. He had tank tracks to help him maneuver over the alien planet landscape. He eventually ate something poisonous, got sick but continued eating samples. Eventually he ate something medicinal and it counteracted the poison he ingested. After that event he decided the job may be too dangerous.
So he keeps taking jobs, going up and up in odds so he can make more money. Every time he takes a job with riskier odds the woman shows she is interested in him more and more. Finally he gets to a job that is too dangerous, he finds himself standing on a pedestal in between wires with his arms outstretch and he is serving as a communications routing system.  As far as he can see, there are other people serving the same function.  He is able to look up his account and sees money pouring in and he says to himself only a couple more minutes and I'll have enough for a lifetime.  As he is waiting he sees one of the other people touch one of the wires running close by and is disintegrated.  Then another and another then he thinks he should go back and he tries to press the ring but wavers a little too much and suffers the same fate as the others.  
Meanwhile back at the office as a woman walks in to inquire about the odd jobs, the secretary turns into a handsome man and awaits the next victim.  
I read it in 1980-1981 and haven't been able to find it in any of the collections I thought it may have been in.  It's a short story so it would not have been a book on its own.

A:

I think you're talking about "Cuestión de oportunidades", by Spanish SF writer Gabriel Bermúdez Castillo. It was translated into English as "Opportunities Galore", and published in "Terra SF: The Year's Best European SF" (1981).
This is a summary of Bermúdez' story:

Ivan Mendoza, devastated by betting debts, goes to a company that gives opportunities: dangerous jobs in other parts of the universe where, the greater the risk, the greater the remuneration. Mr. Mendoza begins with simple tasks, but given his urgent need for money, and the increasing seduction of the secretary, Miss Hollinger, takes progressively greater and greater challenges. Finally, although he has already won the required money, and because he has a betting addiction, he accepts the biggest challenge, but unfortunately does not survive. The last scene presents the next victim, a young lady looking for opportunities, and this time she's attended by a very seductive secretary, Mr. Hollinger.

