With proper work he will lose that ewe neck, gain a top line, have a stronger hind end, and basically gain muscle all over, but there still are the other comformational issues pointed out by the other posters. If your planning on showing soon then pass. He's not physically ready at all, so I would only consider him if you plan on spend lots of time training and working with him. You may not even ride him for awhile, it would probably be better to get him more in shape first by lungening and doing lots of ground work with him before you do under saddle work. Even if he is 'well broke' it doesn't look like he's been worked in awhile.