The real answer is how much you can afford to pay an attorney. If you can afford an expensive enough lawyer and if you have a valid medical license they can get you off with any amount. For that kind of lawyer it costs about $25000 if you contact them after you are busted. If you give the same lawyer a $5000 retainer before you get busted they will still go to the mat and get you off for any amount of weed.

I know this is not the answer you want to hear. I have two licensed people at my house and grow 12 plants. Needless to say I got about 12 lbs of dried buds. For now I can't afford a lawyer at any price so I am pretty careful.

Your point is well taken. Essentially it is legal with a license but the authorities are fighting it anyway. By the way the Feds can bust you at any time regardless of your license.