jesus why do people have to be so difficult. the answer to your question is YES!
(this is all hypotheticial of course)
you can easily grow 3lbs a month with 20 plants soil or hydro. the only thing is waiting the first three months while you split up your plants veg and flower cycles. you can have 20 plants vegging in one room ready to be flowered while in the flower room have 20 plants ready to be harvested.

the first month when your first plants are redy you can cut clones and plant them and still have your mothers veg for a couple more weeks if you want more yield. then in another month take another set of clones from your mothers and put them in the flowering room. So now you have clones that are ready to be flowered every 4-6 weeks. if done correctly you should have no problem getting this kind of yield with 20 plants as long as you pick a strain that is fast growing and keep cutting clones every month.

oh and one more thing you'll obviously need a little extra room in the vegging room for the clones and don't forget dry space.

so ideally to get proper number and decent quality you would need more rooms. but this can be done for sure