This paper studies investment reductions in urban health protection programs in the recent decades under the umbrella of plutocratic ideas. It studies the densely populated slums with little urban spaces, narrow sidewalks, traffic jams, and degraded environmental components. This paper addresses the question of how shall we reopen post-covid-19 cities sustainably and lively? Our method to find a solution is an innovative mathematical model that suggests revision in the current regulations and standards, sizes, and per capita of urban spaces with the help of maximizing necessary investments. This paper analyzes crowded neighborhoods, urban transport sites, and polluted environments where people cannot respect world health organization protocols concerning individual and public health protection. This research aims to maximize investment in public health protection for supplying suitable urban places’ sizes. Outcomes of this research will be helpful to reopen cities in the post-Covid-19 everywhere in the world.