Meanwhile, banks are trying to calculate whether or on what terms they should be lending to the city’s multi-family buildings. A major conference call of lenders several weeks ago revealed lots of handwringing, sources say. One obvious sign is a Bloomberg story last week that said the sale of rent-regulated buildings in the city had come to a crashing half in the wake of the new laws.

Conservative lenders—those that based loans on buildings' net operating income—have the least to worry about in the near term since the new law won’t immediately reduce that income. Loans based on the expectation of increasing rents from renovations or the deregulation of units are much more at risk because the reforms are designed to prevent both from happening.

Speaking of Peter Cooper and Stuyvesant, no one should forget one of the largest real estate financial implosions in history occurred because Tishman Speyer spectacularly overestimated how many units it could deregulate and how much it could boost market rents.

There is also a lot of loose talk about challenging assessments (to reduce property taxes) because apartment buildings are worth less than before the reforms. The last part is true. Market value is determined by the future prospects for rents and profits. But property-tax assessments are determined by income and expenses as submitted by the landlord and analyzed by the Department of Finance. So, assessment challenges filed this year might or might not work.

But over the long term, values won’t increase as much as they would have and some buildings will see their net operating income fall. The Real Estate Board of New York calculated that in five years, assessments will have to be adjusted downward enough to cost the city $1 billion in annual property taxes, although it is expected mayors would make up the difference with higher rates on coops, condos and simgle family homes.

The new rent laws have been portrayed as a great victory for tenants over landlords. Now it’s important to track the collateral damage.