How To Calculate Real Estate Commissions
by Janet Wickell
from http://about.com/

Home buyers and sellers often assume that the entire commission paid at closing goes to one agent, when in fact commissions are usually shared by all agencies who participate in a sale.

How Real Estate Commissions Are Split

Commissions are normally divided, with a portion of each going to the listing office and the selling office. Each office then pays its participating agent a percentage of the total received.

The Franchising Company Gets a Cut

If an office is part of a franchise system, such as CENTURY 21® or Coldwell Banker®, the commission paid to agents within that office is decreased by whatever percentage the franchising company charges.

Some Agents Do Keep More

There are real estate offices where agents pay a monthly fee for brokerage services and office space, and keep all of the commission earned from their closings.

But unless those agents are the listing and selling agent for a transaction, they do not typically receive the entire commission paid by a selling client.
The rent-your-space option works best for agents with an established clientele and regular closings, because fixed monthly fees can be hefty, and each agent is responsible for every expense associated with doing business.