Hmm...while I like the idea behind this, they really need to tell you what kind of horse you need rather than just say horse. Also I think it is kind of crazy to have to use a Warhorse because they are crazy expensive. I mean spending north of 1000 gold for a horse every time you want to upgrade to a cavalry unit is kind of crazy especially when you can recruit cavalry units for like 200-300 gold from towns and villages. You should be able to use any type of horse in my opinion which would make upgrading to cavalry around 100-200 gold give or take if your using the lowest end horse.