If you have your permit, you should know, and understand the law, like the back of your hand. Once you make yourself legal, there is no point in putting yourself into, an illegal position.
A medical marijuana patient, is allowed to have a "caretaker" ie. person to care for him, and his medical needs (that includes producing the medication). As long as you have a copy of the original permit, posted within view of wherever you have plants growing, with a photocopy of his drivers license, your drivers license, and a hand written, or typed, and signed letter, stating the name of the patients caretaker (your friend), and have him sign it in agreement. You should be fine. Depending on what state you are in, your number of allowed plants will vary, but whatever it is, do not go over the limit. If you are allowing your caretake to grow for you, at the caretakers house, anything you do beyond the law (as in go over your legal limit of plants) all the blame will come down on the caretaker, or whos ever house it is.
Another thing, nobody besides the caretaker is allowed to witness anything that has to do with the cultivation, or consumption of the medicine.
Remember, the permit doesnt give you the right to grow it, it only gives you a defense against the law, to prove that you need the medicine.
Good Luck.