Hi Tobin,
You own copyright. It is
NOT a "work for hire" arrangement since you did not sign anything
PRIOR to beginning work (
"if the parties expressly agree in a written instrument signed by them that the work shall be considered a work made for hire...."). See the
U.S. Copyright Office webpage for details. Look under "Copyright Basics" Who Can Claim Copyright? Register your copyright now.
They will require model release to publish. For information about model releases see
"The Substantive Law Behind Model Releases" by J. Jason Sims. If you can, track down the models and get them to sign a model release now releasing the right to reproduce the image to YOU. You can find release forms
here at the NPPA Independent Photographer's Toolkit Photography Releases.
Final word of advice. If you want to be a professional find out everything you can about copyright, privacy and personality rights, contract law and professional business practices. Put everything into writing and get your client to sign BEFORE you begin work. Written, signed contracts enforce your professional status and help to reduce misunderstandings.
Barry M. Robinson