Tony was a regular at the Bar YN worked at. When he was there, he wasn't THE Tony Stark. No, to YN he was just Tones. A guy who would harmlessly flirt with her but listened to her when she needed to vent about life. It was the same for Tony, the Bar, no, YN was his safe haven. YN was someone he could go to to talk about anything. When YN hits a snag in college Tony offers his help which is exactly what they needed to blossom a relationship that they didn't know they needed.