This isn't as cut and dry as if you were getting pain treatment with a manner recognized by Federal law. Your health insurance company may not recognize MMJ and they may not pay any fees associated with that form of treatment. Be prepared for that. You should probably read your insurance paperwork and contact the insurance company directly if you have any questions.
Another thing to consider is health insurance companies usually (from what I have seen with friends and family) do not cover the cost of MMJ either. So even if they do cover the admin costs of joining your state's MMJ program it is highly unlikely they will be providing you with cash to buy it. For people used to 100% health costs being paid, this can be a bit of a rude shock. Maybe you can be reimbursed? But I haven't ever heard of that happening.
Some states allow you to grow your own MMJ but that is not without cost and takes a decent chunk and space of time to do successfully.
Different states have different rules on employers' ability to fire a MMJ patient. Read up on your rights, if any, in your state. There are a lot of misconceptions about the extent of protections given by MMJ legislation. Honestly, in the workplace it usually isn't much. Outside of your own home it usually isn't much.
There are typically a number of resources you can use for research for MMJ in the workplace in your state. An afternoon of internet searching and maybe a few phone calls should give you a pretty clear picture of the rules in your state.