Its a real , legal problem that you need to consider.  The Auralie and tanith models I would not have a problem with being 18+.  Check the license for each character to see if "adult" or porn use is restricted, if not then they are for any legal commercial use. 

You may need legal advice , and I have consulted with the local county DA on some requests.

You can ask for opinions at renderotica, its discussed often because its a terms of service issue.