WP Emember & Zendesk API LOGIN INTEGRATION

I am a Zendesk Enterprise customer with Multi Brand and Guide for 3 ea. subdomains. I want to have only paid subscribers to have access to the Zedndesk Guide Support Portals - so there will be 3 separate websites with a separate login to 3 ea. separate Guide Support Portal subdomains. I would like to integrate with Wordpress WP Emember that would manage the payment and database for subscribers. WP Emember has an API. So there would be a login on each website that would log directly into the respective Zendesk Guide Portal for that site and there would be no general or anonymous access without being a paid subscriber. I am not sure if this should be SSO or something else. Currently I am developing all 3 main websites with the first one launching soon. The others will follow over the next several months.... So if I know what can be done for the first one I potentially could complete the same on my own for the other 2 when the time comes. Is this something that you are familiar with and is it a big deal? Please let me know along with a cost, etc. Thanks, Steve Matzen scm@[login to view URL] 518-326-8000