How do I convince my parents and I'm in eight grade to let my guy friend hang out at my house and he is just a friend?

If they are wise parents they will let you have your friend over, but they would always keep it chapperoned. I say this because I was a teen boy once, and trust me, 999 times out of 1000, a straight male teen isn't into "just friends" with females. He may play the "friend" angle for a long long long time, while the whole time secretly, or maybe not so secretly, wanting a lot more... hormones are a powerful force in teen guys, don't ever put yourself in any situations that you would regret later on. Have your friend over, but don't ever be alone, and especially not in a room with a door shut.