To obtain the instructor rating (class IV) in Canada requires:
CPL-H and
w/ 250 hrs PIC in helos
w/ instructor course
-30 hours dual
-40 hrs ground instruction
Hope I got all the numbers right, I'm going from memory on a couple, but the main point is the 250 PIC req'd, so it cannot be obtainined immediately after the commercial without paying for an additional 200 hours-ish out of pocket. Most people don't have an extra $70K for the PIC plus $10K for the rating.