When you are self-employed, it's up to you to pay your own taxes. The good news is the you are not taxed on 100% of the commissions you recieive each year. Instead, expect to pay taxes on your commssions less any expenses incurred during the year that are "ordinary" and "necessary" in connection with being a realtor.
On your real estate commissions less expenses, you will owe federal income taxes, state income taxes, and another tax known as the self-employment tax. Here is what I wrote is an article a few years back:
You're subject to an additional tax known as the "self-employment tax". When you work as an employee, your employer withholds social security and Medicare taxes from your pay at a rate of 7.65%, and then matches the taxes withheld. So the government gets 15.3 cents for every dollar you earn. When you're self-employed, you're required to report and pay that 15.3% tax, known as the self-employment tax, as part of your federal tax return. (Your self-employment tax rate goes down to 2.9% once your combined salary and net moonlighting income exceeds $106,800 in 2010.)
That being said, we generally recommend that our clients who are self-employed set aside between 33% and 40% of their net self-employment income for taxes.
You can read the complete article called Memo to Moonlighters at: http://www.findagoodcpa.com/2005news/news0205.php.
I hope this information helps you out.