Most CO-OPS require buyers to put down 20-25% of the purchase price, about the same as what most lenders require these days.   But the range can be vast, depending on the co-op—anywhere from 10% down (rare) to 50% or more at higher-end buildings.

Co-ops also expect you to have sufficient money left over (also known as ‘liquid asset requirements’). The required amount can range drastically, from a few months worth of maintenance payments to 1 to 3 times the purchase price of the apartment. Two years worth of mortgage and maintenance charges is about average.

In addition, each co-op will expect you to meet a debt-to-income ratio, usually around 25%-29%. That means your total monthly payments--mortgage and maintenance--cannot exceed the specified percentage of your gross income. An excellent credit score is also required.

Add them all up, and you will find that the average co-op's financial standards are much higher than the average mortgage bank...a primary reason NYC co-ops withstood the last recession so well.
 

While in recent years, some CONDOS have started to require co-op-sized down payments, most typically don't have any financing minimums.  Bear in mind, though, that if you’re getting a mortgage, banks these days often require 20%, unless the building qualifies for an FHA loan, which carries a 3.5% downpayment requirement, or you and the apartment qualify for a SONYMA loan, which has a 3% downpayment.

Many co-ops and condos used to require "borderline" buyers to put an additional one to two years of common charges in an escrow account as insurance against nonpayment. The odds of this happening to you increase along with the perceived 'riskiness' of your application, as measured in debt-to-income ratio, U.S. citizenship status, or a variety of other factors. However, unintended legal consequences of the 2019 rent reform laws appear appear may have ended this practice for co-ops.  Instead, you may be asked to provide a guarantor.