Here's the link to the Craigslist ad:

And in case the ad is gone, here is what it says: "Very sweet tempered 18 year old TB mare, 15.2 hands. Bay with white sock and blaze, I have a very loud Paint filly out of this mare, she has also had several foals that have raced. By Houstin (by Seattle Slew) out of Growing Regard. She ties, clips, loads, stands for farrier, good trail horse. Her price is nagotiable to the right home. I am giving her up for financial reasons. 352-201-8145"

And the mare's pedigree is

I don't know anything beyond what is posted in the ad, but in addition to siring approved stallion Noble Houston, Houston has multiple TB daughters who are Premium mares in a variety of warmblood registries, and several offspring competing in hunters, jumpers, and eventing.