Memberful is a popular service for paid user subscriptions. They have an official plugin for WordPress as well as for Discourse:
erlend_sh (Erlend Sogge Heggen) #1
Payment option plugin
Subscription Module Integration
WP integrate with Discourse and WP paid subscription plugin?
zaino (Zaino) #2
Curious if anyone has used the Memberful plugin and what your feedback is? I have a community in WP and looking to add Discourse with the option of creating paid membership tiers.