Since 2008, our company has sold apartment buildings all across Chicago. Many of the owners we work with are families who bought a building a generation ago, live in or near it, and rent to their neighbors. More of them are calling us to sell, and the reason is almost always the same. The math stopped working.

As the City Council prepares to vote on Mayor Johnson's Protecting Renters Ordinance, that math deserves more attention than it's getting.

Start with property taxes. According to the Civic Federation, Chicago's total property tax burden rose 53.3%, or $2.7 billion, between 2014 and 2023. Rents rose about 41% over roughly the same period. Last November, Cook County Treasurer Maria Pappas reported that the median residential tax bill in Chicago jumped 16.7% in a single year, the largest increase in at least three decades, with far steeper jumps in parts of the South and West sides. This spring, her office found that Cook County tax bills have grown 182% since 1995, about double the rate of inflation.

Taxes are the largest line in a building's budget, and insurance, utilities, repairs, labor and financing have climbed right alongside them. The owner sets none of those prices, and every one of them is paid out of rent.

The squeeze is hardest in the neighborhoods that can least afford it. A building on the South or West Side often can't raise rents to match a tax increase without losing the tenants who live there. When costs go up and rent can't follow, the difference comes out of the building. The roof gets patched instead of replaced, the boiler gets one more season, and eventually the owner sells.

That's usually when we get the call. The buyers for those buildings are increasingly larger investors with compliance departments and attorneys on staff, and they price every new rule and fee into the rent from the first day they own the building. The neighborhood owner who knew every tenant by name, and who held rents flat when a family hit a rough patch, is going away.

Mayor Johnson's ordinance adds to that pile. It creates a rental registry with new fees and with fines that escalate to $500 per unit, each day counted as a separate offense. It restricts the fees owners can charge at move-in, rewrites relocation assistance and lease administration, and builds a new city bureaucracy to enforce all of it. Each provision may sound modest by itself. Together they add cost to buildings whose margins are already gone.

Protecting renters is the right goal. Renters are best protected by a city that keeps its older housing in good repair and in the hands of owners who can afford to keep it there.

If Chicago wants lower rents, the city should start with the costs it controls. That means slowing the growth of property taxes and the spending that drives them, and expanding the Cook County Assessor's Affordable Housing Special Assessment Program to small buildings. It means making zoning and permitting faster and more predictable so new housing gets built. And it means dropping rules, fees and fines that raise costs without improving housing quality or tenant safety.

Most of the cost of housing in Chicago is set by government, insurers and utilities, and renters end up paying it. You can't make housing more affordable by making it more expensive to provide housing.

Michael Thanasouras is the owner of SVN Chicago Commercial, a real estate brokerage specializing in multifamily, retail, office and land sales across the Chicago area.