I'm friends with a local registered sporthorse breeder ($8-$15,000 foals) and another who is a Friesian breeder ($10-15,000 foals). Both are long-time breeders, carefully built up their herd and clientele, and do everything right. They research the stallions, get the mares inspected, and don't breed constantly. Neither makes much money at it and they're happy to break even. If you're going to breed, do it because you love the horses and want to improve the breed, but don't do it expecting to make $$$. All it takes is for one foal to have a major problem or the mare to colic or founder, and it can cost thousands at the vet hospital, wiping out all your profits for the breeding.
One suggestion I would have is to stick to the quality horses such as the beautiful "Esprit" horse that was posted. There is a huge problem with overbreeding the less expensive horses, and the result is HEALTHY pregnant mares and foals sold to the abbatoir bred in such huge quantity & have no acheivements. In my opinion, there is a market for performance horses with good conformation & with parents who are achieving things. Definitely take your little ones to breed inspections and/or halter classes. It's not only good experience for them, it helps build their horsey 'resume' so they're more desirable.
To market, post the ad on all the horse internet sites. For sites you're not sure of, do the free text ad. If someone is really interested, they will ask for photos & more info. Also make a nice flyer for her and when you take her to the shows & breed inspection, hand it out & hang it on her stall. Join your breed associations to network & find sales leads. You don't have to start a whole breeding web site, but you can get a free hosting account and make a nice page for this girl. Add photos, pedigree, videos, etc. (youtube is a great place to store videos)
If it were me, I'd find a good breeder to mentor under. They can tell you who the best repro vets in your area are, if it's worth it to do your own AI, marketing tips, stallions to avoid, best shows, whatever. And you'd have someone good to call for help, instead of having to call the vet out every time there is a question. Perhaps you can get a p/t job working for one and learning the ropes?