I am a freelance researcher working in Manhattan. My state of residence is Florida. It is where I live when I am not working, it's where I have all my mail, paychecks, bank statements sent to. While working in NY I stay in New Jersey. I'm going to start filing my taxes but am not sure which states I have to file for or what the proper way to go about it is. Anybody have any suggestions?

For sure, you MUST file a NY state tax return, because that is where you were physically located when the money was earned.

Depending on HOW LONG you stayed in New Jersey, you may need to file a NJ state tax return as a part0year resident. However, little, if any, tax will be due because the credit you would get for paying the NY state tax return will, more than likely, completely offset your NJ state tax liability.

Florida, of couse, has NO state tax return.