I have a person who has an H-1B status with another company who is doing some work for us. Should he be a W2 employee with us? I read somewhere about a form 129 that needs to be completed. Thanks for your help.

H1-B visa holder can work for multiple employers (full time or part-time) but each employer must file separate H-1B petition. H-1B visa holder can't work as self employed, freelancer or do the contact work in the free time.