I don't think dog training is something you (generic you) can just decide to become. It's not something you can take a class in, and then hang a shingle as a "Certified Dog Trainer." Some people are naturally good at training dogs but can't work with people. Some can work with people and are really good at the sales end of things, but not so good with the dogs! And often the certification isn't worth a whole lot when it comes to real hands on training. Tho I do know that lack of actual knowledge doesn't stop everyone....
There's a woman who lives behind one of my groom clients, she has a gaggle of schipperkes. (aka little black devils) She wanted me to "just" clip their nails for her.....she couldn't do it, her dogs wouldn't "let" her. But she also didn't want to pay what I wanted to charge, so I declined.
A few months later I heard rumors that she is now a certified dog trainer. Sure enough, she had her van wrapped with a fancy logo and business name. From what I've heard her dogs still won't "let" her clip their nails.
--Regina and the GSDs:
UCDX von Sontausen Holy Grail (The BUNNY!) HGH, UD,RA,BN,GN, ASCA UD RAX High in Trial
PAM Monster Mike SchH2,UDX,OM1,TD,RE,VER
PAM FGDCh Ianna von Sontausen UDX,BH,TD,RE,PT (4.26.1998 - 2.11.2013)