My advice would be to try it on your own based on your friend's plan. If you find that you aren't motivated enough to do it that way, though, I would
highly recommend joining yourself. I know it's a lot of money (trust me, I'm a student!) At first I was sure I couldn't afford it, but I eventually realized what I REALLY couldn't afford was to let myself get unhealthy. I would honestly say it's turned out to be the best purchase of my life! And don't worry about spending the money and then not following it; that's what the counselors are there for. It doesn't happen overnight, but they teach you how to stay on plan.
Either way you choose to do it, I know you can be very successful on the program! And you can always come here for advice and support, of course!