While it's true that we all need to start somewhere, there are some animals that are better suited for that learning curve and I don't believe that the horse is a good subject for that. A non-pro does not have the time to devote and the horse is just the wrong animal for on/off training. It's terribly important for a horse in particular to have a solid foundation for an owner to build on.
What animals should s/he start with then? If you have the experience of riding and know your dicipline well, you can't really do anything more to prepare for training a horse yourself, can you? You can't be a pro immediatly.
So.. what do you mean?