deanco: Woah, dude, you just blew my mind. Four factories for 1 store! I'll put farms near cities like that to insure fresh produce and low shipping, but factories! Man, I'm like, 2 factories for 4 products in 2 cities. Doesn't your plan waste...er, boxes? Assuming a simple supply chain, making 1 product might take 4 or 5 boxes, so a factory can probably make 2 products with a little planning. Unless you're saying you have 2 assembly lines for each product supplying 1 store, in which case my mind just got blown again. Guess I'll have to rethink my strategy for the 22nd time...
I'll use a very simple product for an example - the humble bed. It's one of the best early moneymakers in the game, in my experience.
To make a bed, you need one thing - timber. So I put a purchasing unit buying timber in the middle box of the top row. Then I put a manufacturing unit directly under that, and a sales unit directly under that.
Sometimes I'll hook up an inventory unit next to the sales unit. They're inexpensive and can be useful to make sure that production continues when sales are slow, and there's supply when the production can't keep up with the sales.
Now, this looks like an incredibly inefficient factory, using only three (or four) out of nine possible boxes. But pretty soon, provided your timber is of high quality, the beds will get very popular, and the factory won't be able to keep up. So I add another manufacturing unit next to the present one, with links to the existing purchasing and sales units (and the inventory unit if it's there).
And as the demand grows, I'll add a third manufacturing. So the factory ends up with one purchasing unit in the top row, that links to three manufacturing units in the middle row, that links to one sales unit in the bottom row. One sales unit should be enough - with other products it might not be, but for beds it works well.
And this factory will most likely still have problems covering the demand in one city, at least until the results of the training kicks in. Other players might claim it's an inefficient way of doing things, but it works extremely well for me.
It typically looks like this in the end:
# P #
M M M
# S I
Edit: Keep in mind that not all products behave the same - with some products you may easily have one factory for several cities. Also, if you want the bed strategy to work well, you need high quality timber. So buy yourself a good lumber mill and make sure it's set on internal sale so that the AI players can't take advantage of your raw materials.
Edit 2: And yes, this is for one product in one store. :-)