The best way I ever know is http://www.catsnine.com/plans.html They offer WHMCS License with their $9.99/mo plan Regards
I can vouch for Licensepal, they're great. If you ever cancel though make sure you send them a couple of emails, and cancel in plenty of time as they can be a tad slow in cancelling your order/account/license with them.
If you get a reseller through us i can get you a whmcs for $9.99 just come into support and we will set you up,
But then you need to use the WHMCS with their reseller, as you cannot use the WHMCS license somewere else