> But I have to come back to my university after that or the university will kick me out. At least in the US (I have very little knowledge of how college works

> But I have to come back to my university after that or the university will kick me out. At least in the US (I have very little knowledge of how college works outside the US), I wouldn't let this university policy play too much into my decision. A school might make you apply for readmission, but the readmission process generally isn't all that arduous, especially if you were doing well in school before your departure and you left (and stayed away) for good reason. "I have a solid transcript, I left to work on a startup, I stayed for n years because the startup was successful, and now I want to resume my studies" would pass muster for readmission to any school I'm familiar with. If you want some bonus points, maintain your relationship with a faculty member during your absence, and ask them to put in a good word for you on your return. And if that fails, then there are lots of other universities out there who accept transfer students. That being said, I'm not sure I'd recommend a startup if you're not 100% sure you want to do a startup. Even if your company is successful, you're going to have moments where you want to give up. If your starting point is "maybe this startup thing isn't such a great idea," it's a lot harder to power through the trough of despair. (Also, there are the practical reasons other people have pointed out, but I'm not sure that playing your cards conservatively is always the best move).