How much would it cost to build a goat pen?

I'm going to be getting a goat for my FFA project. I can keep it up at their barn but it would be so much easyer and I would be able to spend more time on it if it were at my house. We have land but the only fenced paddock is only hotwire at somepoints the rest I don't know about,and contains a donkey and horse. So how much roughly would it cost to build a pen for a goat? And what type of fencing would I need?