TN Management Consultant - company restrictions?

I'm going to be applying for the TN Management Consultant visa as I've been offered a contract position to be a Management Consultant.

My questions are -

After entering the US with the Visa (providing I am approved at the border) am I also allowed to work as a Consultant for other companies, or am I only allowed to consult for the company that wrote the letter?

Does the company that I work for have to have a minimum amount of employees? And is there a minimum revenue that the company has to make per year? And does the company have to be in business for a minimum amount of years?

If anyone has the answers to my questions above, I thank you in advance for your time.