Event Custom Fields

How do I go about adding a custom field for Events onto the event details/header area?

For example, because there is no capability of creating paid events I would like my user to have the ability to post the cost to join an event if not free. And display the cost very clearly in the header area, possibly next to the event name or event date. Similarly I would like to add a "Register Here" link that would like to another custom field where the Event Owner can provide a link to send the user to, if they are accepting online payments for the event.

Ideally it would be nice to have a Paid Events Application that would support the above features as well as a few other small features and a hand full of the most common payment gateways.

Thanks,
James