H4 visa- can i sign a non disclosure agreement and work as an intern?

[ucinusa]

I have a degree in Science from Canada and am currently on the H4 spousal visa. I have found an opportunity to intern for a fashion designer (not my field but my interest.) They want me to sign a nondisclosure agreement. If I do is that legal? Can I legally do this position bcs it is non-paid and other interns don't get paid either- so it's like studying or volunteer work. right?