I didn't write the law. refer to
Section 333.26424 of the law, paragraph 4, subsection 2:
"for each registered qualifying patient who has specified that the primary caregiver will be allowed under state law to cultivate marihuana
for the qualifying patient, 12 marihuana plants kept in an enclosed, locked facility"
They are cultivating the plants for the patient, therefore the plants technically belong to the patient. This does not meant that the caregiver doesn't receive compensation for the service, but legally the caregiver is only allowed to grow the plants for their patient, they can't legally consume any of the medicine unless they are also a patient.
Nowhere in the law does it deal with the concept of "overages." Caregivers were limited to only 5 patients in order to dissuade anyone from trying to make a huge business out of it - it is supposed to allow patients who need relief from MMJ to hire someone to grow it for them if they don't have the skill or knowledge to do it themselves, not to set up businesses.