It is good Netiquette to use free actors. Do use free actors.
Free Actors Netiquette
Amateur actors do not get paid. Payment is professional. A lot has to do with the intent of the film. Fan films are productions. However, not intended to make money and viewed freely on the Internet or other in outlets.
Free actors make films for a variety of reasons. If the producer must pay an actor it becomes an independant or semi-professional production.
Use free actors because paying them makes a production professional.