I used to be an equine attorney and my opinion is that you do not need one for what you want to do.
Essentially, you want to form a corporation or a LLC (Limited Liability Company). If you Google “LLC” and then your state, you will find many sites which provide the forms and which will walk you through the process.
However, if you want an attorney to do this, a general practitioner can help you.
You can also get forms for your boarding agreement and release of liability forms. Google is your friend. MAKE SURE that the forms give you the language and statutes for your state.
As far as liability insurance, a good horse related insurance agent is what you want. They will know more about your needs than a lawyer will.
If I was doing this for the first time, I would probably buy the forms and see how far I could get before I had questions. Then you can call someone to ask specific questions.
But remember, all of this is state-specific. An attorney in your state can give you correct advice/answers. Do not go out of state to get an attorney just because he/she has a big name.
I would not recommend an equine attorney unless you are involved in litigation having to do with horses. Then, it is very important to use someone who knows the topic.
Mind you, this advice is coming from a retired an non practicing “equine attorney” who very quickly found out that “equine corporations” and “equine liability” had little to do with equines and more to do with forming corporations and buying insurance. The equine part of it was minor.
The information given above is not offered as a legal position on any of the topics addressed. I advise that you consult an attorney if you have any questions.