I appreciate you have been here a long time (at least, judging by your post count) but I'd love to know why you think you are in a position to be able to make broad sweeping statements like this? Having spent time in and around this forum it seems half populated with negative, bitter toads looking down their noses at people for either seeking a route into their beloved adopted country, instead of offering meaningful, factual advice.
Yes, international study is often flogged as a route to PR, there are even organisations and businesses who will kindly take care of your application, your visa, and just about everything you need to get started, all free of charge. Obviously it is not free in reality, I am under the assumption these education institutes such as TAFE pay a sort of commission for these students who are paying hefty figures. i.e $7500 per semester, x4, plus fees.
I personally know people who have successfully gained PR through completing two years of study, due to a combination of the graduate scheme and managing to successfully be "in the right place, with the right trade, at the right time". BUT it is expensive, there are simply no guarantees, and I would not even attempt it with a family to support or no fall backs. Even in an ideal scenario, I'd prepare to go in with the mindset that there will be no outcome beyond qualification, enjoy the course and continue to work along side your studies. Even if you do study say, carpentry, complete your two years, even complete your 18 months graduate visa, you have to be prepared to lodge a full application with all the associated risks and costs. Begging the question of whether it was even worth studying internationally in the first place as opposed to studying in the UK for example, where it is significantly cheaper.
My partner has considered doing her masters degree here, but the costs are phenomenal. We are fortunate enough to have a permanent home with family while we are here (WHV), have significant savings and no children. But even then it is looking extremely likely we will not bother.
In short, can you get PR from TAFE? Yes. Will you? Probably not. Is it worth $30k to roll the dice, condemn yourselves to 24 months of short working hours, being skint and trying to play the mysterious game that is the Australia migration system? If you think so, go for it.