How long before you're considered a resident of a state?

Regardless of your 'residency' or 'domicile' State IF you earn money/income in a State you will most likely have to file State Income Tax forms with each State.
As to taxes.....that would depend on amount of monies earned.

This is something you would need to research each States residency & possible tax consequences.

After tax season is over.....make an appointment with any H&R Block Agent.
Will cost you a few bucks but they can access each States requirements.