A setup to do some sort of job on the side is possible but you will need partners.
I work as a hospitalist and one of my colleagues started up a group that rounds on patients in nursing homes. He is palliative trained and has an interest in this so he got some of his buddies to start a business with him and rounds with him on their varying weeks off. He loves to work and is always doing something so keep that in mind. You're free time will dramatically decrease and he told me it was a huge financial upfront cost forming the business, getting insured, and having a lawyer he trusts to do the legal paperwork.
It can be done but it all depends on your non compete clause and your hospitalist contract. If you have a clause that says you cant do something like that then its not even worth looking into with your current job.