Nov 17, 2012 12:02PM PST
At the moment, events are either ticketed events or free/RSVP events - there isn't a way to blend the features into a single event, although we will be changing this soon.
For now, the best way to do this would be to create 2 separate events: 1 event for your core audience that you want to be able to come to the event for free, and a second event that's ticketed so your core audience can buy tickets for their guests. The first event, for your core audience, would be setup as "RSVP only" meaning people will not need to buy tickets. The second event would be setup as a ticketed event. In the description for the first event (RSVP only) I'd add a note letting people know they need to buy tickets for their guests and provide them with a link over to the ticketed event page.