Do You Have To Be 18 Years Old To Sign A Lease Agreement In New York State?

This matter falls under contract law.  

In contract law, one of the requirements to determine whether the contract is a legal one is called "competence".  In contract law, the term "competence" means the legal capacity to make a contract.

In New York , as in many other states, people are ruled competent to make contracts if they are over 18 years of age (the age of majority), providing they have reasonable mental faculties intact.  A minor who makes a contract can rescind or void it, with one general exception, and this is where your daughter will run into problems:  A minor contracting for "necessities" is bound to pay for their reasonable value. A "necessity" includes food or shelter.  Your daughter is likely bound by and liable for her lease, even though she was 17 when she made this contract...