Give your friends a free month of Office Hours by sending them a link like this one:
https://markbutler.com/register/refer/[your custom slug here]/?discount=firstmonth
Watch this short video for a step-by-step guide to setting up your custom referral link with the built-in free month.
Oh, and be sure the email address on your profile is one where you can receive PayPal payments.
(Tip: you can have multiple email addresses on the same PayPal account.)