All agents are different. You can pay upfront a small fee with an online agent, or opt for the no sale no fee. Agents work on different percentages. It could be as low as half a percent, to 2 percent or more. Have a Google search for online agent fees and you will see you can pay very little to sell your home, in comparison to some high street agents. Whether you get as good a service is debatable. But many use all the main sites like Zoopla, Rightmove etc. Most interest comes from the main portals.