It all depends on what you want to do and whether or not, as mentioned, you have the financial backing. Also, are you planning on employing people and working yourself or are you planning on running it yourself.
There are a lot of things to think about. I would suggest as a start, you get a trail riding place together along with maybe some beginner lessons by yourself (if applicable) or you could hire an instructor. But, this is only how I would start. As mentioned, there is not a lot of turnover at these places and many fail. I used to work at highlands equestrian centre here in australia and even with all the agisted horses (who were there @ $170 a week), the complete range of lessons and trail rides, they still struggled every week. It is a hard business as costs are so high therefore most money made goes back into paying for the horses, the food, their shoeing, public liability insurance and the list goes on.
Think and plan and take your business plans to an accountant or the like and they can maybe help you out a little with the financials as this will be one of your bigger, initial issues. (not just initial though, this will be a constant issue.)
I do wish you the best of luck with it all and im sure with a lot of planning, researching etc you could make a perfectly acceptable establishment :)
Start small and go slow. Like the previous post, make sure you have enough money to support everything your doing without making a dime. It will probably take at least several years to start breaking even. That's if your very smart, organized, hard working, and lucky. :) Think of it awhile first and be very specific about what you plan to do.