On June 14, 2019, the Housing Stability and Tenant Protection Act (“HSTPA”) was enacted in New York State, marking a significant shift in rent regulation policy by closing loopholes for deregulation and strengthening tenant protections. While the law has reduced speculative opportunities, it has also provoked strong opposition from landlords who had invested in rent stabilized properties under the expectation of future deregulation-driven appreciation. Five years after HSTPA’s passage, this paper evaluates the impact of HSTPA on the sales prices and investment patterns of rent stabilized buildings in New York City. By drawing on property transaction data from multiple city agencies, this study employs a quantitative approach to assess shifts in market behavior. The analysis offers insight into the effectiveness of HSTPA in reshaping investor strategies and stabilizing tenant protections, while also highlighting market tensions and uncertainties that remain in the rent stabilized housing sector.