68 Pa. C.S. § 4301
An association must be organized prior to the date the first cooperative interest in the cooperative is conveyed to anyone other than the declarant or an affiliate of the declarant. An association may be organized prior to the date on which the real estate subject to the provisions of this subpart is acquired. Immediately upon creation of the cooperative pursuant to section 4201 (relating to creation of cooperative ownership) and at all times thereafter, the membership of the association shall consist exclusively of all the proprietary lessees or, following termination of the cooperative, of all former proprietary lessees entitled to distributions of proceeds under section 4217 (relating to termination of cooperative ownership) or their heirs, successors or assigns. The association shall be organized as a profit or nonprofit corporation, trust, trustee or partnership.
68 Pa.C.S. § 4301