I am wondering if it is possible to create a membership site and only have members see content from when they sign up and going forward? In other words, if someone signs up in August is it possible to only show them the content from August going forward?
Yes, this is possible! You can use the bundle feature for this. Every month you can add the new course into the bundle and remove the course from the previous month. In this way existing members will still get access to all the previous content but new members can only see the courses starting from the month they sign up. It requires a bit of manual work but you can definitely set this up!
Hope this helps!