Can my boss make me work for another company for free?

I'm working at company A, and my boss has allowed a few employees to create an entirely new LLC (Company B) doing largely the same work. They're a completely separate LLC basically selling different things. Think of a Honda dealer deciding to let a few salesmen sell Toyotas on the side.

Apparently I'm going to be expected to work for this new company, "Company B," doing the same tasks I do for "Company A." If I'm not going to be getting a paycheck from Company B, can the owner of Company A require me to do these tasks?

1. Paid a salary. As long as salary per period divided by hours worked per period exceed the minimum wage, yes.
2. Paid by hour. As long as your are paid for each hour and paid any statutory premium hours, yes.

Ask your boss for your employment documentation. You need to be clear who you are working for so that all of your taxes, unemployment compensation contribution, social security, etc… Are being paid properly on your behalf. If your boss intends for you to keep working for Company A, with paychecks coming from Company A even if the work is done for Company B, then you still need to make sure that Company A is really ok with all this. If this is by some agreement between Company A and B, you should just do a good job no matter what you are working on. Work hard, get positive performance reviews and move on when the time is right.

The problems will arise if Company A doesn't know their staff is being used for Company B on Company A's dime. This would involve fraud or maybe embezzlement. Also, you could have problems if you receive checks from Company B without proper employment documentation. You might wind up as part time for each and lose your full time status, or Company B might not pay taxes on your behalf properly.

You have every right to have your employment status clearly documented. Send your boss an email asking them to clarify everything in writing. If they won't do it, call your state's department of labor and ask them what to do. You might need to file a complaint.

Are you saying you are being asked to work without pay? If yes, then NO.

If you are getting paid you are not working for free.

Employees can be lent or leased.

Pretty much everyone's job description has an "other tasks as assigned" clause.

If you don't want the job then quit.