My understanding is that rental is not allowed, except for transition training with an LOD (letter of deviation? might have the wrong initials).
Co-ownership is allowed. That could be an equity club, but be careful about the club route to assure that you're not busting the ownership rules. You can't have a "club" where one or two people own the plane and 10 "members" fly it.
Disclaimer: This is my understanding of the rules and is subject to clarification.