It means they havnt beed riden since they raced. You sound like a beginner. I wouldnt recomend getting a OTT (off the track) TB, as you wont beable to comtrole it. Thats why the price is so low, because it need to be re-eduacted. Yes they will act completely different. All they know it BOLT-FLOAT OUT!!! When you buy a OTT you need a lot of exerence to ride safly.. It is a long time of flat work, troting/walking and an inexperenced rider wouldnt know how to put the horse into proper work.
This horse has not only finished racing 8months ago but mostly hasnt been riden at all (spelling). If you were to buy this horse, you would want to be a really good rider, it is not a first or second horse by the given information. Also if it has only finished racing this year it would be young as well. I would as not onlt look at price and height but education, age and temperment are some of the most important features when buying a horse.
Myself... Ive seen ppl make that mistake