A one off set-up free may be payable when you join up with your broadband provider. These charges offset the cost of the work required to link your connection to the provider's broadband service.
For new cable customers this will involve an engineer visit to install the cable connection to your home. For ADSL customers work still needs to be performed at the local exchange to enable broadband on your line and/or route your broadband signal to the new provider.
Although these setup fees aren't usually massive (often under £60), if your budget is tight they can be quite unappealing.
Keep in mind that broadband is a long term investment, so try not to compromise your choice of a quality, value for money package by focussing too much on a one-off payment. Having said this, the broadband market is very competitive, so if you think you've found the right package but don't want to pay the setup fee you can always make this known to the potential provider. They might agree to waive or reduce the fee, especially if it's for a 12 month sign-up.