What are the chances of getting through the U.S border from Canada as a Canadian citizen?

I know this 34 year old guy that wants to be with his girlfriend in U.S. But, has a criminal record from when he was18. The charge was careless misuse of a fire-arm. This guy hasn't been in trouble for any thing for at least 15 years and can't afford a pardon or U.S entry waiver. He just wants to see his girlfriend a.s.a.p. My friend plans to travel from Canada to the U.S and is going to by car Alberta and plans to arrive in Kansas. Any tips would be great! Thank-you.