I think you may be speaking of Chiropractic work. Massages *should* be allowed anywhere.
I got my massage education through our local college. It is easy to learn and it is a nice thing to be able to do for your own horses. Making a living at it is also an option. You must be very dedicated to it in order to make consistant money. When I was still massaging on a regular basis, I charged $50/hour. That is pretty cheap comparativly. I only charged so little because I did it so infrequently, it was difficult to build up a client base. It is physically a stressful job and until you get your hands in shape, your hands will ache a lot. Its really worth it though.
The only thing I don't like about Equissage and other programs like it is they give you the option to 'learn at home' online. This really is a hands on job and its hard to learn unless you know exactly what you are looking for. My instructor had us going to several local horse rescues donating our time to learn the proper way to massage. Until you feel the knots, you really have no idea where they are and what kind of symptoms they cause. I can tell you if you horse is fighting the bit and pulling the reins from your hands when asked to go on the verticle that it most likely has a poll knot. I can tell you exactly where to find it and how to get rid of it...but its difficult to pin point because a knot can be pea shaped or like a yarn string...and sometimes it doesn't feel like much at all. I would go to a hands-on class if at all possible.