Your friend doesn't know what he's talking about. Rattlesnake venom is extremely potent. Even IF you get to a hospital, it depends on where you've been bitten and how long the venom has been in your body. Once it reaches your heart, you're forgeted. In lucky cases, you might not show symptoms for an hour, but just generally you don't want to be bitten by a rattlesnake. Especially not you, as you're probably under 18.
Usually rattlensnakes bite you in the leg or hand, depending on how you approach them. And yes, i know how potent it is, and by depending on how close we are to the hopital.
And you know nothing, you show symptoms right when you're bitten, because the vemon dissolves your flesh, and it spreads out. It takes at LEAST an hour to get to your heart from your palm.