Dentistry? What is the job satisfaction though?
Math has high pay + no dealing with screaming kids (unless you do teaching ...)
Or check out these guys resumes. They have like, 1 degree if you add up all their courses. Plus like, a hundred billion dollars...
I think you want Accredited Certification, which is Civil (or maybe other) + 3 years experience. But it depends on which state you live in, and stuff. You have to check yourself really.
http://www.bpb.nsw.gov.au/certifiers/index.shtml may help.