It all depends on the project, whether this is a single item or a combination of items.
Let's take the first instance. I am making guns and military gear, so we'll presume that the item in question is a gun.

1. You need to do research and gather your documentation together --two to four days.
2. Decide on the way to tackle the project in question and do some rough drawings plus a list of the parts you need to make --two days.
3. Modelling. Depending on the complexity of the object --four days to two weeks.
4. UV Mapping --One day
5. Texturing --One to two days.
6. Rigging for Poser --One day.
7. Testing in Poser --One day.
8. Promo "pretty pictures" and PNGs --One to two days.
9. Readme and presentation text --One day.

So, you can say that it will take a minimum of two weeks before your gun (of average complexity) is ready to hit the market.
For more complex projects the time-table varies of course. For example, I've been working on my last product ever since September and it is just finished.... :)

I hope this gives you a general idea.

Panos

"That's another fine mess you got me in to!" -- Oliver Hardy