I cannot access the site you listed but I am guessing you are thinking about working for a place that writes essays for students. True, this is not an honest way for the students to get their grades but there is no dishonesty on your part. Plus, your friends are not paying you bills so they cannot find fault in your work.

I say go for it. In fact, I think it will be interesting. Think of all the different topics you will have to research and how much you will learn along the way. I may apply myself.