Depending where and what you want to buy you may not have to go through a broker. There are many units for sale by owner here on TUG, on RedWeek and others. I have 2 I'm giving away listed in the classifieds and in the forums, as do many other TUG members.
eBay is another good place to find bargains.
The important thing to do is to make sure you know exactly what you are buying because there are so many different types of deals out there. Weeks, RTUs, points, and others.