It's not the right tone to take when talking with a stranger. So it would be a red flag if someone considered it appropriate to adopt that sort of language in an introductory email.

Maybe people are more relaxed about this sort of thing in California, but what that language would suggest to me that the applicant is young, male, and probably not very well-read (use of colloquialisms like "ain't" is another red flag). Right away I'd assume them unable to handle copyediting and communication work.