I'm 5'4-5'5, he's 17.3hh plus....?

I think he is a great horse, and I don't think you would look to small on him. The only problem I see is that in all his gates he swings out with him right front leg, This could mean a lot of things, He toes in, he toes out, or he has a crooked knee. All of these conformation faults could mean he will not hold up well. Especially because when looking at big horses 17hands+ good conformation is crucial because their added size makes them break down so much easier. If he was a 16h horse I would not worry about it but since he is so large and has such a big build I would defiantly get a vets opinion. Also he is a WB so he has a larger chance then a TB to have OSD so you would defiantly want to get a full vet check with X-rays and Radiographs, (could be over 1,000 usd ) I don't know if you are a kid or not but he is in Canada and his price is in Canadian dollars so he is more like 20,000. I personally do think he is too expensive for such a BIG green horse with what look like to be potential issues