OK

So, you want to produce 3 lbs every one month.

You need 2 rooms.

First one is all blue lighting like Fluorescent or MH. You start your ?? number of plants in room 1 to grow them to the desired height. This alone takes anywhere from NO time(if you throw clones into flower and have no height to grow in), OR can take a year to grow a large bush.

Only you know what space you have is my point here.

A standard plant in someones grow room MIGHT reach 2-3 feet before they start it flowering. That takes around two months.

THEN, when you put it into flower under the HPS lighting you can move it to the flower room. This room does nothing but 12/12 under the red light of HPS. Each plant needs around 2.5 square feet of floor/table space for light penetration.

Once in this room it will take anywhere from 55 days to 12 weeks to be finished.

Humidity, nutes, temperature, CO2, lighting and strain will determine your yield.

The only way to produce that amount EVERY month would be to have four rooms going or a large enough flowering room with lighting to have two stages of flowering or do what most do and accept that this takes around four months to complete a grow and finish one every two months while running two stages. Grow and Flower.

Basically I think your question is far to broad to really answer. You want 5000 lumens per square foot. I don't remember the PAR numbers.

I read a thread about a SOG grow. This guy puts rooted clones directly into flower. He starts five clones every week. After 8-12 weeks he had around 3 ounces every week as long as he started new ones every time he pulled finished ones.

Point is,.. Every grow is different. Every strain is different. Your schedule is REALLY different.

So kinda hard to say on what you've given.

With lots of money and lots of space you could produce 3 lbs every week. You'd have a lot of plants going on different schedules though.