I don't blame you, medicine is a terrible field now, it's been completely ruined by insurance agencies and hospital administrators. But you could still make money in medicine if you have a private practice you can hire doctors and focus on expanding your patient pool. If you're going to be generating passive income it can be hard to do under the table because all of the companies you get involved in will be sending you checks. If you're going under the table with the companies they'll probably screw you over and you'll have little recourse.