The rule of thumb is 3-4 weeks from the time you apply for an NJ Mortgage to the time a commitment letter is generated. This timeline however can be improved if your lender is running efficiently and you are able to provide any documents quickly when requested. It also could be improved if there is a waiver for your appraisal, which is determined once the lender runs your application through the automated underwriting system from Fannie Mae or Freddie Mac.