Double Ending a Deal in Apartment Buildings - How is it done ?

[Daniel Johnson]

In Los Angeles  a  large percentage of apartment buildings are sold Off Market, so its hard for me to know if listing agents are representing sellers and buyers (double ending the deal) Im sure thats the case tough,

but when it is listed on The MLS you can clearly see many listing agents double end their deals,

and Im wondering how its usually structured ?

1. Is the Listing agent procuring a buyer and the seller paying both commissions

2. Is the Listing agent just listing and will not co operate with other agents when selling to a buyer 
(OFF Market)

3. Does the listing agent expect the buyer to pay their own buyers side commission ?

4. Does the listing agent get commission for selling, procures a buyer but the buyer pays no commission and the listing agent still helps the buyer with the purchase agreement (without representing the buyer)

What is a likely scenario here ?