Rent-free living? What's the catch?

When her mom gets a new boyfriend, 19-year-old Su-Hyun decides to move out. In a stroke of luck, her college classmate Yu-Jin offers for her to move in for free, no strings attached. But Yu-Jin has a hidden motive... Will her secret affect their dynamic as roommates?

(Source: Manta, edited)

Note: Chapter count includes a prologue