When you purchase a theme from us, if you've paid by credit card or actual PayPal funds, as soon as the transaction is cleared, you can access your AppThemes customer dashboard and download the theme from there right away.
What you actually need to use the theme though is your own hosting account (you may wish to read about our hosting promo here:
http://www.appthemes.com/resources/wordpress-hosting/). Your domain name points users to your website. On your hosting account you will install an instance of WordPress, on which the theme is installed. Here are the installation instructions to give you an idea of what is involved:
http://docs.appthemes.com/jobroller/...ith-jobroller/.
Users must register before they can post, and yes you can have paid job listings for employers (more information is also on the setup documentation page linked above).
If you are looking for a developer for hire to help install and setup JobRoller for you, please note that we have a certified partners page here:
http://www.appthemes.com/partners/. Thanks.