Any advice for a college student looking to make some money on the side via online business?

I'm a college student currently and I've been wanting to make money yet getting a job is very hard with my schedule and even my parents say I should just focus on school since most people I know do. However, I want to make my own money and i've thought of business ideas before but they'd all require 100% of my time. I'm thinking I should start an online business where I can sell things on the side and maybe when I'm done with college or if I want to continue the route I can expand. But right now I feel the need to make money since most my stuff is paid for(I have credit card) and it's just not the same spending money when you know you didn't make it yourself.