Hell, I can sing too, but the purpose of this is to make sure he shares whatever money he wins using your voice.
I buy professional microphones, for musical purposes, considering I'm a composer, so I like to experiment with my own voice too. My mic. is worth a bit over $200, and works very well, and will not break. It is very sound sensitive, but you can use settings for the mic. to remove the ability to sense breaths, background noise, etc. I forgot the brand though, as it doesn't have the brand, well, branded on the model.
By the way, Nitro, there is most likely an age limit. If there isn't, then fine, but remember; if you use someone elses voice, the submission technically isn't yours (at least, not the entire thing). So whatever money you win (if you win money), I suggest coming up with a written agreement with whoever decides to do it for you, stating that you split the money either 50/50, or 60/40 (60 being whoever sings for you). Seriously, when it comes to matters like this, many things can happen, so be careful, as the land of television advertisement is a dark and horrible place.