If your 13 then no one is going to help you with purchasing an airsoft gun. Also, if your parents don't buy the pistol for you then your not going to be able to walk into a Canadian Tire and purchase it (if you didn't already know). Also, having that for backyard target shooting would be o.k but you will not perform well if you try and play with it against anyone else (never do so in public places).
In terms of danger, there is a certain amount of danger involved with almost any sport, as long as you take precautions you can significantly minimize the risk. I would suggest at your age (if you find a field to play at) choose to wear full face protection covering the mouth and ear. Make sure you are also wearing ASTM approved goggles. Protective clothing is also recommended.