Business for World of Warcraft

My dad wants me to get his character to a level 40 on world of Warcraft. He's willing to pay me 100 dollars for it. I told him to just go on one of those websites that you pay 40 dollars to get to a level 40 which is way cheaper and I don't even have a level 40. I'm gonna get my character to a level 40 first and then get him a level 40.