You need to tell us who issued the medical marijuana card and the circumstances. Also, be aware, those cards are still not being fully honored and recognized for federal law purposes, and only apply in the state where issued. Even a valid card can be ignored by the federal authorities and you can still be prosecuted under federal law.
First, no one in this forum can give you legal advice, We can talk about general law and procedure. However, to get legal advice, you need to hire a lawyer, take all your paperwork in and let the lawyer know everything about your situation. If you hire that lawyer, she or he may be able to give you actual advice.
Second, most real criminal defense lawyers will not give business advice. We handle case once there is a criminal investigation, an arrest or charges are filed. Since we are not giving prospective advice on how to conduct business, we can maintain an inviolate attorney client privilege with our criminal defense clients. Lawyers who give advice on what someone can or cannot do are subject to having the attorney client privilege challenged.
This is not just academic. We are representing people who grew the number of plants under the circumstances recommended by lawyers whose advice is now being challenged. There is even an effort on the part of the government to discover the emails and communications between the lawyers and these clients.
Having said all of that, possession of marijuana -- and cultivation, transportation and furnishing of marijuana -- is a federal crime. Further, state authorities can decide to interpret or reinterpret practices that seem to be tolerated one day and are the subject of a major raid the next. So, any lawyer who says, "no problem" to cultivating marijuana is making a guess as to whether or not it will lead to prosecution.
You should talk to a serious lawyer who is willing to advise on these things. Whether or not the lawyer thinks marijuana should be legal, you need someone who will tell you the truth about the risks.