This paper examines how “incumbency bias” in housing policy—reflected in measures like restrictive zoning, certain rent regulations, and property tax incentives—can limit opportunities for newcomers. Drawing on Rawls’s veil of ignorance, the analysis develops four principles for housing justice: universal access to adequate housing, protection against arbitrary displacement, enabling mobility for those seeking better prospects, and ensuring long-term economic and environmental sustainability. I show that when these principles clash—for instance, if efforts to protect current residents restrict others’ housing choices—policy outcomes tend to favor incumbents at the expense of newcomers. To address this tension, the paper proposes a Principle of Fair Housing Opportunity, calling for reforms that balance the legitimate interests of existing residents with the needs of those who wish to relocate. The aim is to show that recognizing the significance of both stability and mobility offers an important corrective to the existing literature on housing justice, which tends to focus on the harms of displacement and gentrification. I discuss policy reforms that would reduce incumbency bias and promote equitable housing access without dismissing the concerns of existing communities.