There are several factors in whether you can make a livelihood in horse body work.
Some are about you and some about your local market
About you; are you actually good at the technique? Just as important can you communicate what you are doing to the human client? Can you effectively market yourself? Do you have existing connections?
About the market: as one of the posters said, are you in an affluent enough area that people pay for these extras? If you are how many people are already offering horse body work? How will you distinguish your services?
I live in a relatively affluent horse area in a metro area where humans are very interested in alternative therapies. But it also seems like almost every week I come across a flyer FB post or business card for yet another person who had taken a short course in one of the Equine body work modalities.
I already know a very good equine massage therapist and another bodyworker who does chiro alignment. I don’t pay much attention to the newbies as when I get a bodyworker out I have identified a problem and want results for my $100 fee. I would prefer to pay $100 and get a confident diagnosis and a fix than $50 to be a learning experience for a newbie.
However I am not sure how much of their income either of my bodyworker earn from that. One seems to have an organized route through the big barns and travels with a show team in winter. The other one I think has several money earning projects on the go.
I doubt many folks make a full time living from.this.