It's totally okay to crush on someone you don't really know. I've done it a few times, and I am now.
I agree with Alex Moore., it's no fun to have so many what-ifs floating around in your mind. I say talk to him, maybe get to know him a bit, and then try to decide if you really like him.
You should never take the chance of ending up with all these; what-ifs. So yeah jump, and maybe fall flat on your face sometimes, I bet there will be enough times you land on your feet too.