How long can you live in a new state without changing residency?

Laws of individual states may vary, but as to New York state, a New York State resident is defined as a person who lives in New York with the intent that New York be their "fixed and permanent" place to reside.

Evidence of Residency - A person who lives in a home, apartment or room in New York state for 90 days or more is considered to have "presumptive evidence" that she is a resident of New York.

Establishing Residency Under New York state law - a person has established residency in New York state when he pays New York state taxes and has a New York state driver's license or identification card, a New York state voter registration card and bank accounts within the state.