Here are some sentences about Leo's student life using "used to" or "didn't use to":

1. Leo used to get up late every day before he learned to manage his time better.
2. He didn't use to have any money, so he had to budget carefully for his expenses.
3. Leo didn't use to have a job during his first year of studies; he focused solely on his coursework.
4. He used to share a flat with friends, which made his student life more enjoyable.
5. Leo didn't use to sometimes study in the afternoon; he preferred studying late at night.