When you work for free in the film making business, it will not be because you don't need or want to get paid. It will be because you are trying to gain experience and be able to find work in the film making industry. For one thing, you need experience to be hired in the film making business, and to gain experience you need to have worked in the film making business. It is a vicious cycle and most of the time the only way to break it is to intern or volunteer to work for free on a project.
This can actually lead to paying job on the film maker's next project if he likes your work. This is a great way for a film maker who is on a tight budget be able to work with a production crew. And whether the film is a success or a flop, the knowledge needed to find gainful employment will be yours when the shoot is done. You will be able to add this experience in your resume to show that now, you have the experience needed to be a paid worker on the crew. If you worked hard as an intern on one production, but the film maker did not hire you for his next project, you should not worry too much. You will be able to show the experience you have gained and have at least a fighting chance to get a paid position.
If you enroll in a film making school or University, you will see that an internship with a film maker is part of a four year course of study. It certainly isn't inexpensive to take a four year course at a school. Deciding to work on a film making crew as an intern, will be one of the best choices for you, if you have no experience in the film making industry and want to rub elbows and make contact with people who know the business inside and out, and they may be able to point you in the right direction. You will even find that some production companies will pay their interns minimum wage.
Investing your talent and know how in an internship will build your resume and network so that down the road you will be hired for the position you desire. You may want to intern more than once to really add to the experience on your resume. This is not a free ride for you, you must show the film maker that you are serious about working on the film, and are up for the position. Do network with the crew to aid you in finding a paying job after your internship is through.
If you find the work too grueling, the hours too long, and you just aren't getting in the swing of things as you should be, maybe it is good that you learned this early. Above all, no matter how new you are to the film making business, always act in a professional manner and you will find you will be on your way to a great career.