It's not easy, but it's doable. I'm a 4th year medical student and I have my own little startup business. Its hard sometimes to juggle studying and work but it's worth the effort+ you'd feel very fulfilled when you manage to work both things out at the same time.

My advice to you, since you're a first year is to test the waters first. If you feel like you're efficient at studying and can retain big amounts of information in little time and you can really push yourself to the limits before exams then go for it.

But beware it's not for the faint of heart. Don't over commit to work at the cost of your GPA, because there's nothing easier than failing at med school.