The Master for Clinical Psych is costly (and very selective) - basically, Masters that lead to improved position&salary cost money, sort of as an investment.
I believe that with a PHD one can also prescribe but you’d need to check.
Typically the Master&PHD are done at the same school, NOT the same university as for undergrad for cross pollination purpose (ie., meet new professors, discover different research projects, study with different approaches…)
A PHD that is not funded is not “serious” - if they see professional promise they’ll fund you. A PHD is full time work - very long hours. There’s no time to work on the side.
To work as a professor you need a PHD (though with a Master you may give 1 class at a CC as a professional -but that would be a VERY poorly compensated side-gig).