Zoom Webinars and number of users

Hi!

My company is looking into getting Zoom Webinars. It looks like it's an add-on. What do I need to have first to then add on Webinars? 

Additionally, is there a limit to how many different log-ins can host a webinar? My boss would like us all to be able to host, as she doesn't like using her own computer. 

Thank you for any assistance!