In the skittish modern credit climate, lenders look as closely at the building as at your financial history and income in deciding whether to give you a mortgage.
Building-wise, lenders require that anywhere from 15% to 50% of the apartments in the building must be in contract. The exact percentage is up to the lender, and so-called “preferred” lenders are typically at the lower end of this range. Preferred lenders, named in the offering plan, become intimately familiar with the development and don’t have to start from scratch as an outside lender might. This minimizes the possibility of the loan being denied because of issues with the building though it doesn't rule it out; the lender may decide at some point to put a cap on the number of units it is willing to finance, for instance.
Before issuing a mortgage to a buyer, lenders also require that the building have a Certificate of Occupancy or Temporary Certificate of Occupancy issued by the Department of Buildings.
Most lenders require that you put at least 10% down on your new condo; the average is around 10-20%. If your building is FHA-approved (more and more common in many emerging Brooklyn neighborhoods, for instance), you will only need to put 3.5% down.