I'm a graphic designer, and for clients who have little to no website experience, but want something professional, I'd recommend Wordpress. You can use wordpress.com for free, but if you want to use some of their other features it costs money--in that case, if you're willing to take the time to learn it, I'd use wordpress.org. I'd recommend getting a domain from Namecheap and finding a host or using a free one like one of my favourites, Freehostia (you have to make sure the host supports PhP and mySQL for wordpress to work).
Wordpress.org has great installation instructions, and I think Freehostia and a few other sites have an instant install option that does it all for you so that you don't even have to worry about setting up your own database--it does it all for you. The only tricky things you'd have to deal with is setting the nameservers up for your domain, but it isn't that bad :) And wordpress is great because there's an endless amount of professional, customizeable templates, and plugins to manage your business. It looks like some of these options others have posted are good as well! Or find a website designer... because there's nothing as bad for an equestrian business than having an unprofessional looking website without adequate information, trust me.