[What you need to know to start the day: Get New York Today in your inbox.]

When a neighborhood landlord named Stephanie Kirnon learned about the far-reaching changes to New York’s rent laws, she grew anxious: How would she afford the $29,000 in repairs to the leaky roof of the 26-unit apartment building she owns in the Bronx?

A few miles away, Gloribel Castillo, a lifelong Bronx resident who works two shifts as a cleaner in Manhattan hotels, received a text message saying that the rent measures would be approved by the New York Legislature. She felt immediate relief, knowing that the $1,430-a-month rent on her three-bedroom apartment could no longer be sharply increased .

The tightening of rent regulations approved on Friday by the newly emboldened Democrats in the Legislature represents one of the most sweeping interventions by government in the New York City real estate market in decades, establishing new rules for millions of people on everything from rent increases to security deposits to evictions.

And the epicenter for the impact of the changes could be the Bronx, the borough with the highest percentage of rent-regulated apartments, and where the landlords and tenants have offered conflicting visions about how property owners and tenants will be affected.