If you're just starting, you usually do "time for prints" sessions. In other words, the session is free, you get prints of the pictures, but the photographer still owns the pictures and will be the person getting paid if the pics are sold. Of course, I've also heard of photographers charging for the session, so depends on the photographer. You also usually have the option to purchase your pictures, which gives you the right to submit them to mags for payment. However, I think the mags really only take pictures submitted from photographers seriously, unless you're a known model.