i am a psychotherapist in private practice and wish to create a group practice.What type of attorney should i seek to create an agreement

A psychotherapist would form a professional corporation under the Moscone-Knox Professional Corporation Act. See California Business & Professions Code § 2995.  Even if several psychoterapists form a limited liability partnership, it may be advisable for each psychotherapist to operating under a professional corporation.  Consult with a business attorney for a full consultation.