Dina Bologa was shocked when she learned in July that the rent for her Jersey City, N.J., two-bedroom apartment would go up 40% to more than $6,000 a month if she renewed her lease. She thought about moving and tried negotiating with her landlord. Then Ms. Bologa’s neighbors, who were facing similar rent increases, started organizing, the Wall Street Journal reported. They filed petitions with the city saying that the 19-story waterfront building should be subject to rent control. The city’s rent-control administrator agreed. As of late August, the landlord could raise rent in Ms. Bologa’s building by no more than 4% a year. “When they go to these crazy numbers…people say, ‘Really? Can they do this? Are there no laws that limit anything on rent?’” said Ms. Bologa, referring to her landlord, Equity Residential. A spokesman for Equity Residential said it uses rental-pricing software and market comparisons in lease negotiations. The company plans to operate Ms. Bologa’s building under rent control in accordance with the city’s ruling, the spokesman said. Skyrocketing rents are prompting cities and towns across the U.S. to consider enacting rent control to keep prices in check. But in communities where these tenant protections have long been on the books, many residents aren’t aware of them or find that enforcing rent control is no easy task. Residents often don’t have the resources to pursue rent-control enforcement or are worried that they could lose their homes by fighting their landlords, said Brian Rans, attorney for the Jersey City-based nonprofit the Waterfront Project, which provides free legal assistance for housing and other civil issues.