Does anyone know if the built in helpdesk for WHMCS is accessible to unregistered (potential clients)? What if someone wants to submit a ticket before purchasing? Am I limited to email with WHMCS support options?
Yes, it's accessible to potential clients. When they submit their question via the contact form with WHMCS, it creates a sales ticket (provided that you've created this department) in which a link to the ticket thread is emailed to the potential client. Same with emails piped to WHMCS.