Cost To Own A Hirse Per Month?

I want to buy a horse but I want to make sure I would be bale to have enough money to proerly take care of him/her every month so I was wondering if people could tell me how much is cost them a month roughly. Also, how many times a year does a hore have to be dewormed? And how often? What does it cost roughly? When does a horse get accinated each year and roughly how much does it cost?