You should be sixteen or eighteen and over. Stallions can be very dangerous and hard work. They are hard to handle. If you are a beginner buy a gentle mare or friendly gelding. When you go to look at stallions to buy, pick out a few you like. After picking out which ones you like, test ride them. Your stallion may learn manners from a elderly gelding or other horse.
The value of a stallion relies on certain things, some examples are breed, how well trained, if he sides good foals, and how he behaves. behIf you have other mares and you don't want any foals don't pasture him with them. If you have another stallion do not put them in the same pastures they might fight and seriously hurt each other.