The short answer is NO!  The detailed answer applied to the past would be "Very Rarely," and only under unusual circumstances.

Is Jim a dual agent?

No, he is not.  A dual agent, theoretically, represents both the buyer and the seller.  Jim never does this.  When he works with a buyer, he only represents the buyer and the buyer's interests.

Has he ever accepted a listing? 

Over the years, Jim has worked with many buyers.  Some of these buyers have lived for a number of years in the house that they had purchased with Jim's help.  Understandably, it is not unusual for people he has worked with in the past to ask him to list and sell their property when they decide to move on.  Under this circumstance, in the past, Jim might have accepted the listing -- but even then he usually arranged for the property to be listed by another company.  Here are three examples:

• Example 1: Several years ago, Jim helped a buyer purchase a condominium apartment for her retirement.  After she moved into the apartment, she asked Jim to list and sell the house that she had moved from.  Because was the resale market unusually "hot" at the time and the aparatment was lileky to sell very quickly, he accepted this listing, then advertised and sold the property for a good and competitive price.
• Example 2: In 2006,, a buyer whom Jim had previously helped buy a home, passed away unexpectedly.  The family knew about Jim and the help he had provided their relative as it had been mentioned several times in the past.  They wished to have Jim be the listing agent for this property.  Under this circumstance and because of the established history, Jim agreed to accept the listing.
• Example 3:  A friend whom Jim had helped in the purchase of two investment properties wanted to sell one of them and asked him to list the property for sale.  Jim reviewed the circumstance and made several suggestions for preparing the property to sell.  However, ultimately he referred the listing to another company because he believed they would be very effective in marketing the property -- and this proved to be the case.

Jim's primary work is as an Exclusive Realtor Buyer Agent.  His professional life is devoted to this work.  At the same time, with more than 24 years in real estate to build on, Jim is occasionally called by people he has worked with in the past when they decide to sell their home.  As a Buyer's Agent, he does not actively market for listings.  In the past and only under unusual circumstances he has occasionally accepted a listing from someone he has worked with previously.  In all cases, these past listings were from past buyers -- from friends -- or from family members. This has happened rarely.