How many membership levels can I have?
As many as you like :-) There is no limit.
Four Membership Levels Not Enough?
The s2Member Framework (the free version) is limited to a maximum of 4 paid Membership Levels. With s2Member Pro you can create and label an unlimited number of Membership Levels. Of course, you can also use Custom Capabilities for added flexibility—where Custom Capabilities are not associated with any incremental access like WordPress Membership Levels are.