Of course, your oc has a life outside of being a hero, student or civil worker. Considering my hero academia is a pretty futuristic universe with plenty to do, it's best your oc has some likes, dislikes and interests! This is optional, of course, and these are just some small things to give your oc some more depth

What's their favourite/ least favourite food?

Which heroes do they idolise / hate and why?

What their favourite/ least favourite colour?

Where do they come from in terms of ethnicity?

What area do they currently live in / lived in before they went into the dorms?

What's their favourite/ least favourite thing to do?

What do they do in their spare time?

Who's their friends?

Tbf I don't think there's any limits. Any random little ideas you have about your oc are good for development, so write them down somewhere. Also, about the heroes part;

Keep in mind that if they're a huuuuuge fan of these heroes, make it make sense. For example, it'd be perfectly fine for someone to have a room stuffed to the brim with all things Mt Lady, as she's a popular and well-known hero. But if you oc had done their research and knew of more underground heroes like Eraserhead, don't give them too much stuff of him as there wouldn't be much. Maybe a poster or two or something like that. But just think about the heroes popularity before making your oc a fan of them.