Nobody here is really qualified to answer that.
1. It will depend on state laws.
2. It depends on the nature of the photo.
3. It depends on whether or not your use can be seen as commercial or not; i.e. are you using the photo for a pormotional purpose with the end goal of making money.
4. It depends.
A few good resources:
Property and Model Releases | American Society of Media Photographers
Model Releases
Apogee Photo Magazine: Model Releases, A Primer
Model Releases and Your First Amendment Rights | Black Star Rising
Model Release FAQ - Lawdepot.com