That is not a 1500 dollar horse, maybe a 500 dollar horse at most. You can find plenty of green or hard to handle horses. A 6 yo that requires an experienced rider is either a pain in the butt, or never been trained. Your question leads me to believe he wouldnt be a good match for you.
But to answer your specific question no reason he couldnt carry you. With proper conditioning a sound horse isnt going to have an issue with anything approaching a normal human load.
Doesn't seem like a good fit ... I think its the way the ad is worded doesn't seem like it would work.. .as for the horse he would be able to handle the weight but would need to be conditioned to get used to alot of riding with the weight like any horse and rider does.
"Natural Horsemanship would be a big plus with this guy."
Read this: " This horse is nervous and reactive, so you better take it slow with him."
I agree with above. Pass on him. BTW, it's tough to find anything safe for a new rider anymore.
Are you anywhere close to Oklahoma? You could contact CHERIE and see if she has anything suitable. =D