There is no final test to apply to the facts, just the best argument which can be made for either side. Much depends how you document and describe the relationship. Surely the training, both in time and general overhead, is not "profitable". If the intern then performs according to the training on a confirmed and written basis that no compensation is to be derived other than training and curicullum building experience, there should be no problem under many factual circumstances.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
The criteria concerning whether an individual is an intern (thus need not be paid) or an employee (thus must be paid at least minimum wage) are discussed in the post at the link below.
A lawyer would have to analyze your situation in light of the six criteria identified in that post. It is impossible to provide a definitive answer on Avvo.
This information does not constitute legal advice and does not establish an attorney-client relationship.
Mr. Schultz is correct. There are no straight forward cases in this matter. Each is different. Your case will need to be analyzed by an attorney. If you do not have attorney, your local county Bar Association may be able to set you up with a free or low cost consultation with a qualified attorney in your area.
See my blog here: http://www.lowenthallawoffice.com/2012/10/unpaid-internships-101-california-unpaid-internship-standards-and-regulations/.
This response is not intended, nor should it be construed as legal advice. Any information provided is for educational purposes only. To schedule an appointment for an attorney-client privileged consultation, contact me at 530-231-4949 or visit our website at www.lowenthallawoffice.com. The exchange of communications through Avvo.com and similar social media does not establish an attorney-client relationship with me or my office. Thank you.