If you want to do music therapy, you're going to have to bite the bullet and take the equivalency courses and do the internship in order to get certified...they won't let you take the test without the proper training. Art therapy is a little different in that it is usually a Master's level program and is more psychodynamic. I think California Institute of Intregal Studies (CIIS) offers a degree in art/expressive therapy.
I don't have my degree in music therapy specifically. I have a BA in music from SJSU and took the equivalency courses in music therapy at UOP, and now am currently in the Masters program in music therapy. I don't recommend getting another certification in, say, expressive arts therapy (CIIS offers that btw) and then calling yourself a music therapist....an MT-BC will read you the riot act if you do! :P

Have you thought about taking out a loan or doing FAFSA or investigating scholarships? If you apply to UOP as a Masters student, then you can get financial aide and take the equivalency classes, and with that be able to take MA level classes.

Check out the Certification Board for Music Therapy for more details (www.cbmt.org)

Good luck and blessings!