Those who do not audition into a faculty studio can study with upper level Conservatory students who are being mentored by their own teachers. There is a nominal charge (something like $10 per hour lesson) but no academic credit given for student-led lessons.
A slight correction: if you audition for lessons, you will be placed with a faculty member or a student. Either way, you receive 2 credits and the lessons are free. If you sign up for lessons without auditioning (e.g., on a new instrument), or if you can't spare 2 credits for lessons, you'll receive lessons with a student for no credit, at a fee of $7.50/half-hour. (This is based on my experience auditioning for piano lessons last fall; I've been told lessons on other instruments are arranged the same way.)