its all contractual. easily done. think of commission only salesman with no benefits. tons of those guys out there. some only get paid 10 or 20% of the take. good luck!
from the bizzaro trading archives: no need to work for free, pay me and trade my account AND keep 25%!!! http://www.elitetrader.com/vb/showthread.php?threadid=165188
I think the law states that you can only work for free (volunteer) if you are working for a non-profit. Or if you are an intern. I do not know the specifics of what defines an intern.
Don't do that, doing so is just reducing the perception of your competency. The only reason for a company to hire someone is the company has a problem to be resolved and think that the person can solve their problem. So focus on making yourself for being seen as very skillful and reliable for the company.
The idea of internship is that the intern is paid by knowledge and experience in return for his/her work, that's why it is done mostly by young people and for limited time only. 200 years ago a stonemason "intern" worked 4-6 years for nothing learning the ropes before he was allowed to become a mason and practice the skill for full pay.....