I did a lot of work trying this in different ways, and you can do it. If you get cheap milk, it can reduce the cost of the pizza quite a bit. And the secret really is rennet, get the real stuff, not Junket, and it can work... but...
If you use pasteurized/homogenized milk, it might not always work, it will work most the time if you are gentle. But even if it does work, the cheese won't melt on the pizza correctly. It will come out rather hard, it will taste fine, but stretchy gooey cheese it will not be.
You need to get really good milk, that hasn't been homogenized, and if pasteurized, it was done at a low temp., only 145deg., not the usual 165-185deg. This milk will be more expensive, and harder to find. Also it can't be old, sitting on a self for a week, it will degrade to useless. But if using the better milk, this will be more expensive then just buying mozz.
But I've made mozz. with Straus Milk from Petaluma CA, getting it right off the truck. And it was the (still is), the best mozz. I've had. I liked it better than buffalo mozz. from Napoli, but maybe I'll get it trouble saying that...
So, I've gone back to mostly using bought mozz., and only once in awhile, when I have time, make mozz. from Straus Milk.
